'65 GMC 1500 project. From the Netherlands [Archive]

Prowbar

February 3rd, 2021, 11:37 AM

Hello,

A while back I bought a '65 GMC 1500. It is a California made truck that I bought here in the Netherlands. It has the 305E V6 and the SM420 transmission.

I've been looking for a 60-66 Chevrolet for a while, with either a straight 6 or a V8. When I stumbled upon this GMC I figured they swapped the engine, because I've never heard of a V6? After doing some research I discovered these interesting line of engines and decided to take a look.

The V6 runs great, the rust on the truck minimal compared to others that you see. The main point is the bed, it is in rough shape. The bed wood is gone, along with the bed strips. There are tons on bondo on the bedsides, to cover up dents and damage. The fact that the bed is sitting on wooden planks tells the story. There is a generic bed liner sitting in the bed, but there is nothing underneath. The cross beams are luckily still included, they are laying in the bed.

The brakes are non functioning, most of the rubbers are gone. A lot needs attention. I believe the original color to be red. A blue was on top of the red, and they later painted it black. The title that I have mentions the color blue.

Due to space restrictions I decided to park the truck in storage until I start working on the truck itself. We've taken off the bed from the truck to start the fabrication work required to bring it back in better shape.

I'm not planning it to be a show truck. I'll see what I'm going to do about the paint.

The main points are:
-Getting the bed back into shape so that it can be mounted back in the truck.
-Brake work, keeping the drums but upgrading to a dual master cylinder from a '67.
-Checking the engine, possible carburetor rebuild. Converting it to LP fuel. Ignition upgrades.
-Electrical, such as wiring to the lights, dash gauges.
-Changing the sealed beam lights to light that accept H4 lights as sealed beam lights are not allowed here.
-General maintenance.
-Possible repaint in the original color.
-Required welding work.
-Rustproofing

I've bought the X-6523 GMC truck maintenance manuals from Rockauto.com, they sell reprints for a fair price.

This is my first project and I'm learning as I go. I'll be sure to post the progress.

Thanks for looking! David

Prowbar

February 3rd, 2021, 11:45 AM

Some additional pictures.

Prowbar

February 3rd, 2021, 11:55 AM

Here are some pictures of the bed removal and the subsequent rust repairs.
There are a couple of rust spots, all in the bed side behind the support beam, these get full of wet dirt and eat the metal away. I'll probably modify the support beams to let the water/dirt escape instead of trapping it there.

GMCTom

March 1st, 2021, 10:30 AM

Prowbar

March 1st, 2021, 01:17 PM

Hi David.
Welcome to the forum. At the moment I'm also restoring a 1500. I also thought about swapping the V6 at first, but after doing some research I decided to keep it. Not everyone here in Europe has it.
Have fun with your GMC and stay motivated :-)
Tom

Thanks Tom, you have an impressive build going on. Mine won't be a frame off restoration, just fixing what needs to happen. Are you going to run it on gasoline? Gasoline isn't cheap here, thats why I'm converting to LPG. (Liquid Propane Gas)

GMCTom

March 1st, 2021, 03:16 PM

Thanks Tom, you have an impressive build going on. Mine won't be a frame off restoration, just fixing what needs to happen. Are you going to run it on gasoline? Gasoline isn't cheap here, thats why I'm converting to LPG. (Liquid Propane Gas)

Yes, my plan is to run it with gasoline. In Austria it's also expensive but not so expensive like in the netherlands. I think nearly 1,30€/liter (normaly I'm a Diesel driver) but I think I will not drive more than 2.000km/year with my GMC.

Prowbar

March 24th, 2021, 05:32 PM

Quick update. Still busy with the bed rust repairs. I've welded a new section underneath the front panel. The welding work on the bedsides is mostly done, except for the angled sections with the square holes for the bedwood. These still need to be welded in.

I'm also working on the bed crossmembers, de-rusting them to prep for paint. The small cross strip that is mounted just before the rear axle has some deep pits and rust holes, new sections will be welded in. the rest has pitting also, but is still usable.

I'm going to buy a stud welder to help with the dent repairs. I've ordered bed strips and bed bolts. I'm looking around for pine wood the bedwood.

While keeping an eye on the local marketplaces I've scored some parts: cab rubbers from polyurethane (for a C10 so the rear mounts won't fit however), patch panels for the front fenders are new brake shoes for the front brakes.

A local shop that specializes in american cars had a Felpro gasket set for a 305 V6 for sale, how cool is that? Paid 50 euros for it, great price.

Prowbar

March 24th, 2021, 05:34 PM

More pics

Prowbar

March 24th, 2021, 06:12 PM

Pitting in the small crossmember + electrolysis to loosen the stubborn rust scale. Then a wire wheel on an angle grinder. After some rust converter primer they are ready for paint.

Prowbar

March 30th, 2021, 09:08 PM

Well, sometimes things do not go as expected. A fire ravaged the place where I worked on the bed parts and had stored them. Luckily the pickup (without bed) is stored elsewhere, so I'm lucky I still have it.

Its not my house, but that of my grandparents. Glad they are OK themselves. That is the most important. Sheet metal can be welded onto or replaced.

The bedsides were not great but I'm guessing they are scrap now. It seems the tailgate and front panel and still salvagable. The fenders too, but you can't see 'em on the pictures but they were there also (resting against the post with the vise). 2 of the crossmembers were also in the fire, one looks usable but the small one is all twisted up. In the pictures one can also see a couple of Opel 6 cilinder CIH engines. Also a couple of VW 1.6 diesels. All burned up too.

Some pictures:

Ed Snyder

March 31st, 2021, 12:43 AM

Well, sometimes things do not go as expected. A fire ravaged the place where I worked on the bed parts and had stored them. Luckily the pickup (without bed) is stored elsewhere, so I'm lucky I still have it.

Its not my house, but that of my grandparents. Glad they are OK themselves. That is the most important. Sheet metal can be welded onto or replaced.

The bedsides were not great but I'm guessing they are scrap now. It seems the tailgate and front panel and still salvageable. The fenders too.

So sorry to hear about your loss of bed parts, David. Thank goodness your grandparents are OK. Like you said, sheet metal can be replaced. Not so with grandparents.

I have no idea what European wrecking yards are like, but perhaps you could find a Chevy or GMC bed in one of them. I even bought a whole Chevy pickup one time, just to get the bed off of it for a GMC project (already had a good tailgate), then sold the still running pickup minus the bed. Some future owner could always build a flatbed for it. At least it sounds like you've still got a good GMC tailgate.

Prowbar

March 31st, 2021, 02:10 AM

So sorry to hear about your loss of bed parts, David. Thank goodness your grandparents are OK. Like you said, sheet metal can be replaced. Not so with grandparents.

I have no idea what European wrecking yards are like, but perhaps you could find a Chevy or GMC bed in one of them. I even bought a whole Chevy pickup one time, just to get the bed off of it for a GMC project (already had a good tailgate), then sold the still running pickup minus the bed. Some future owner could always build a flatbed for it. At least it sounds like you've still got a good GMC tailgate.

Thanks for the reply Ed. Unfortunately European scrapyards aren't close to the level of 'goodness' American scrapyards are, most cars are empty shells unless they just got in. Finding a 60-66 pickup would be impossible unless it had some kind of accident damage - maybe. It is always worth looking around of course. Here in the Netherlands we have a couple of scrapyards that specialize in USA made vehicles.

My other game plan was to get a set of repro bedsides. They are available, and from what I've seen on the Brothers Trucks youtube channel, they fit proper and seem to be of good quality. I might start a thread in the bodywork section, pretty curious what other folka experience with these is. Hopefully they are a step up from the chinese non fitting junk. They are pricey though so there is that. As for shipping, we have a shop specializing in US pickup parts, they import parts from the USA. Meaning shipping costs would not be an issue here.

Maybe good sections of the original bedsides can still be salvaged - we'll see.
The tailgate is rare, glad to have it, hopefully the warpage is manageable.

Not planning to go with a flat bed - I like the original/factory design the best.

David

WE7X

March 31st, 2021, 06:39 AM

Wow! So sorry to hear that!
Fire is a terrible thing to go through.
I lost a 6 person shop due to fire about 30 years ago.
Nobody getting hurt is a major plus. Tools and 'stuff' can be replaced but loosing a house and a shop space is a huge loss.
Best wished for the family and the projects.
Rod J
Issaquah, WA
1970 GMC RM-7500 410M

Prowbar

March 31st, 2021, 08:47 PM

WDShaffer

April 26th, 2021, 01:07 PM

I just purchased a GM-licensed repop tailgate from LMC. Test fit was perfect. I did spend a day sanding off the finish and applying an etching primer.

Prowbar

April 26th, 2021, 05:25 PM

I've also ordered new repro bedsides and some other bed related parts. I'll try to rescue as much OEM parts as possible. Heard good things about fitment so I went for them. Bought them through a supplier here in the Netherlands. One gentlemen here offered a OEM bed for me but unfortunately can't cancel my repro order now.

Meanwhile, I'm working on the brakes. Cleaning them up and rebuilding the wheel cylinders and brake hoses. New brake lines are also on the list. And a conversion to the dual master cylinder.

All the drums look excellent, shoes are not worn much. I've boiled them to get the muck and leaky brake fluid out of 'em. Wheel bearings and seals are as new. All the brake line nuts broke loose without a problem. All bolts came loose without an issue too, makes working on these much more enjoyable. Thats great about a vehicle that has always been in a dry and hot environment.

Prowbar

June 7th, 2021, 11:55 AM

Hello all, sorry for the lack of updates.

Every week I try to spend a couple of hours working on the GMC. School has been very busy so unfortunately not much time to work.

Anyway. I've done the following:
-Drained the old diff. oil and cleaned up the gunk inside the diff. That oil must have been 30 years old. Gears look very good. 4.10 rear. Replaced the gasket with a new one from Felpro.

-The rear wheel seals wore a groove into the steel sealing surface on the axle. I ordered SKF Speedi Sleeves (no. 99240) and installed them.

-All brake components have been cleaned and rebuilt where necessary. I still have to replaced all the brake lines and convert to the dual master. Ordered DOT 5 silicone brake fluid to be used.

While I was waiting on brake parts I've tackled the propeller shafts. What a mess. On of the u-joints was completely cooked - including the press fit bore into the prop shaft. Also the center bearing must have had a poor press fit, resulting in a rubbing motion of the bearing on the shaft. Aka it was worn undersized.

To repair the center bearing I've machine the worn area round and true to the splines. Then machine a bushing that I split. The 2 halves fit exactly on the machined area. Welded these split bushing on the machine area, and them turned those down for a light press fit with the center bearing. It took some doing but all is well. A very satisfactory repair.

The one press fit that was ruined due to the bad u-joint had the ID filled in with weld. it was then bored out for a new press fit. That worked out good as well.

Then replaced the center bearing with a new one from SKF and all the u-joints with new ones from Moog. Reassembled the whole kitten kaboodle and found out that the grease fittings were inaccessible because I had them facing the wrong way (should have faced the grease fittings to the axle itself :pullinghairout:). So I turned all the u joints around and she was done.

I've also taken the WW carb off and I am rebuilding it. The throttle linkage with the butterfly valves has some play on the shaft. I will ream out the holes and solder on bushings to be turned down with the proper fit.

On the topic of rear axles - what does one recommend for the rear axle wheel bearings regarding lubrication. Mine came out greased. I figured the rear diff oil would lubricate them. Should I grease them, or dip them in diff oil, or fill the hubs with diff oil?

Prowbar

June 7th, 2021, 11:59 AM

More pictures.
1st picture shows the complete Speedi Sleeve. I removed the radii piece (as is possible) with used the bearing to carefully tap it further onto the sealing surface.

2nd picture. Guess what is wrong. Took that one while I was lying underneath the truck, installing the driveshaft for the first time.

3rd picture installed center bearing.

Prowbar

June 7th, 2021, 12:07 PM

4th picture: cooked u joint.
5th picture: worn area caused by rubbing center bearing.

James

June 9th, 2021, 12:18 AM

On the topic of rear axles - what does one recommend for the rear axle wheel bearings regarding lubrication. Mine came out greased. I figured the rear diff oil would lubricate them. Should I grease them, or dip them in diff oil, or fill the hubs with diff oil?

A full floating rear axle is lubricated with the rear end oil. If someone put grease in the hub bearing it was because the oil seal was leaking. Installing the Speedi Sleeves should take care of the problem. On my truck I cleaned the grooves and filled it with Devcon Titanium and sanded it down smooth. Have over 6300 miles on it and no leaks. When you fill the rear axle raise one rear wheel as high as you can go to allow the rear end oil to flow into the hub. After 30 minutes or so do the other wheel. Then recheck your rear end oil.

Hope this help.

Prowbar

June 9th, 2021, 07:03 PM

A full floating rear axle is lubricated with the rear end oil. If someone put grease in the hub bearing it was because the oil seal was leaking. Installing the Speedi Sleeves should take care of the problem. On my truck I cleaned the grooves and filled it with Devcon Titanium and sanded it down smooth. Have over 6300 miles on it and no leaks. When you fill the rear axle raise one rear wheel as high as you can go to allow the rear end oil to flow into the hub. After 30 minutes or so do the other wheel. Then recheck your rear end oil.

Hope this help.

Sure does James, will do like you instructed here. Thanks.

LEWISMATKIN

June 10th, 2021, 03:04 AM

also, when you do your final fill, place your thumb over the lower 1/2 of the fill hole and fill the rear axle untill the oil runs out over your thumb, then reinstall the fill plug.

Prowbar

June 10th, 2021, 08:13 AM

also, when you do your final fill, place your thumb over the lower 1/2 of the fill hole and fill the rear axle untill the oil runs out over your thumb, then reinstall the fill plug.

Could you tell me why you would 'overfill' the axle like that?

LEWISMATKIN

June 11th, 2021, 12:47 AM

so that oil will migrate down the axle tubes and continually bathe the wheel bearings in oil. I have seen too many rear axle bearings and axles destroyed due to lack of lubricant.

Prowbar

July 26th, 2021, 05:15 PM

Hello, another update.

To sum up what I've done so far:

- Filled the rear axle with diff oil, using the instructions given here. No leaks from the diff cover and wheel seals so far :upyes:

-Rebuild the Stromberg WW carburetor.

-Cleaned out the oil bath air filter

-Pre-bent all the steel brake lines for install, copying the old lines, with a couple of extra lines for the dual master conversion.

-In the process of painting the frame with a rust convertor/stopper and then a proper chassis/frame paint.

-Repaired the wiring harness that runs to the taillights.

-In the process of installing H4 lamps. These are required here as the original sealed beams are not allowed in the Netherlands. The connectors are pinouts are the same so they are easily installed and could be reverted if needed.

-I will be saving the original GMC tailgate and rear fenders (if possible). They are now at the sandblaster to remove the baked on paint from the fire.

-In the process of rebuilding the deluxe heater. It will be powder coated black and assembled with fresh gaskets. The heater core is still good and the blower motor could use a little oil on the bearings.

-In the process of performing all sorts of interior related work. From glove boxes to heater controls.

- Forum member AZKen, is helping me out with a ton of parts that will be needed for the build. Much obliged Ken.

Prowbar

August 1st, 2021, 02:24 PM

Here are the installed H4 lamps. I bought them from a fellow that sold these lamps to be used in American cars with sealed beam lights. Unfortunately they are of crap quality, made by Autopal in India. I have to modify them, remove the built in parking lights. Also he supplied 4 regular beam instead if 2 low and 2 high beam. This is needed to properly install them in the mounting bezels. The spacing for the 3 prongs mounted on the back of the light is different on low vs high beam so they don't interchange. Aka this had to be modified.

Anyway, cleaned all the connectors out first and installed everything with a dab of dielectric grease and all worked the first try. :upyes:

Also received my new repro bedsides and panels. Very excited to have them. The boxes got a little wet during transportation but the moisture never touched the panels. They look really good. After the frame paintjob and brake lines the bed can be build up on the truck.

Prowbar

August 4th, 2021, 06:30 PM

Prowbar

August 4th, 2021, 06:35 PM

Some shots of the inside rockers and floor. The drivers side inner rockers is pretty rusty. But overall condition (regarding rust) is still mint compared to some I've seen.
There is some kind of old undercoating left in some places underneath the cab, the light grey stuff. There are also a lot of dirt deposits, these are as hard as rock. To get it off I'd have to beat it off with a hammer and screwdriver. But it did a great job protecting the metal underneath from rust, believe it or not.

Prowbar

August 20th, 2021, 06:03 PM

Still working on the frame paint. Due to other people wanting to use the car lift, it had to be on and off. Which allowed me to complete the whole dual master cylinder brake system and my reproduction of the original tailpipe.

The new brake system uses a repro master cylinder from a '67 C10/1500, which is filled with DOT 5 silicone brake fluid. The whole system is based upon the original regarding line placement, and there is an extra set of lines running to the front right wheel. The original T-sections are all used, and I made up extra brackets to hold the extra brake lines in place. If one wanted, this mod would be easily reversible and it looks like factory, with is what I like. See pictures.

The tailpipe is welded up from a straight piece of 50mm (almost 2 inch) pipe and two 90 degree bends. I tried to replicate the original tailpipe as closely as possible. It angles down a little and exists at the same spot. See pictures.

The tires that came with the truck had tons of dry cracks and were swollen in some areas. Running the DOT codes on the tires told me that they were made before I was born! The newest one was from 1998, my birth year :ahhhh:

Scored a good deal on some new Toyo tires, 235/85 R16. I had them install the white lettering towards the inside.

Also did a lot of rustproofing inside the cab. All the areas with surface rust were covered in a light layer of roestfixeer, the stuff I linked previously. Areas that are double walled or bolted together, and the threads of screw/bolts recieved a coat of Mike Sanders Rust Prevention Grease To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? ( To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? ). I apply this grease generously, while its cold. When it gets hotter is starts to creep between the sandwiched panels, creating a 'live' rust protection. It also works wonders in door bottoms. Just about any place where it is not exposed to the open elements. I plan apply this whenever I can, when I take something apart and reassemble it is given a coat of grease.

Also. Underneath the bench I found a strip of duct tape. Never thought anything of it, but when I pulled it from underneath the seat I found out it was the original 'sales poster' which was taped to the window. It had the original salles price (3500 USD) and a phone number! Will give that number a call ASAP. Hopefully the original owner is willing to tell me the story on this one!

Prowbar

September 19th, 2021, 02:35 PM

It's been a while. Got the frame all painted. Had to move the truck to a new location, so another project (VW Bus Type 3, not mine) could use the car lift.

Recieved a whole lot of parts from AZKen, thanks again Ken.

Have not been able to call the owner, for some reason it keeps saying the person is not accepting calls at this moment. Maybe they blocked me because it is an odd number? Not sure.

What I've done so far:
-Frame fully painted.
-Cab rustproofing. Rust converter on the floor, both sides, underneath the dash and in the doors. The doors were then sprayed with a layer of Mike Sanders grease. Also used underneath the dash and on screw threads.
-Rebuilt the alternator with new bearings.
-Rebuilt the heater controls. Repaired the arms that broke off, installed new heater knobs. Went through the switch for the fan, cleaned all the contacts.
-Rebuilt the wiper motor.
-Installed and cleaned the wiper switch as the original was missing.
-Installed a new fuel sender.
-Re-lubed the speedometer and cable as they were dry, went through all the dashboard lights and gauges. Made a new lens for the turn signal as the bulb had gotten too hot and melted the lens.
-Installed a new wiring harness for the turn signals. Still have a ground issue in one of them, need to make the tool as described in the manual to remove them and clean the contacts.

In process:
-Deluxe heater box powder coat
-Door locks repair
-Dome light install
-Reassemble the doors after rustproofing, still need the window seals as they are gone.
-Wiper arms and hinge rebuild
-Glove box install.
-Rebuild the light switch and rheostat.

There is much more to do, of course, but I hope this gives an idea of what is going on at the moment. So far all the electrics are working first try, except for the one ground issue, got to love it. Of course I try to clean all the contacts and connectors, and reassemble with dielectric grease.

These are great trucks to work on. Got to love all the high quality and perfectly rebuildable components. Also, everything says 'MADE IN U.S.A.'. Makes you feel a little patriotic, even as a non-American. :teehee:

Prowbar

October 16th, 2021, 03:30 PM

Here are some pictures of the mentioned repairs, such as the heater lever repair. See pictures.

Some other things:

Converted VW LT van front door checks into usable door checks for the GMC, since the originals were gone and are basically engineered to fail. These have the added bonus of having 2 extra detents for in tighter spaces.

Rebuilt the light switch and installed the dome light.

Finished the rest of the interior, such as the new glove box, wiper switch and inside mirror. Still waiting on some new parts such as the heater hose and the window seals, should have these Monday. Then I can finish the doors and final points of the interior. Also waiting on parts for the turn signal switch.

Repaired the bench seat, one seat bolt was missing the the caged nut on that side was missing also. Turned a new cages nut and welded it in. Also repaired the bench seat angle adjustment, which works like it should again.

Had the heater box pieces powdercoated, save for the cast zinc/Zamac piece, because of the expected warpage with higher temperature. I also had the squirrel cage powdercoated, which I regret because it threw the balance off. Going to rebalance it with a little setup.

Original blower rebuilt, soaked the bearings in oil, remade the little rivets that hold the bearing assembly etc. Runs good now.

Rebuilt the sliding window mechanisms, installed with new rivets and grease.

Still need to remove the gas tank as the plastic filler neck is cracked, have a new one from steel on order, will replace the hose also. Going to remove the gas tank to gain access behind there to fully rustproof the rear of the cab.

When that is all done, I can focus on getting the bed built up.

Prowbar

October 16th, 2021, 03:41 PM

Also took the valve covers off top inspect the PCV valves. What a mess. Makes sense, it being a farm truck. The last oil change was... well, it will be changed out soon anyway.

Cleaned up most of the mess and gave the PCV valves a good soak in solvent, they look to be in proper condition. Had the breather element replaced earlier with a new one from Wix. New rubber valve cover gaskets, as the cork remains on there were almost turned to stone.

Still have to adjust the valves, no pushrods were bent so that looks good.
Will change the oil when I take off the oil pan to repair that nasty dent and inspect the oil pump pickup.

The oil I will be using is 20W-50 with high zinc (ZDDP). To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

Also added some pictures of the rebuilt blower motor and powder coated heater box.

jagarra

October 22nd, 2021, 04:32 PM

Another oil with high zinc is the Lucas brand of Hot Rod Oil, available at Summit, I am using 20/50 high zinc in some of my flat tappet motors.

Prowbar

October 22nd, 2021, 05:56 PM

Another oil with high zinc is the Lucas brand of Hot Rod Oil, available at Summit, I am using 20/50 high zinc in some of my flat tappet motors.

Ah yes, the Lucas is available here as well, but much more expensive. I know the Lucas should have a higher ZDDP content (I believe around 2000 PPM), this MPM stuff runs around 1200 PPM I believe. We'll see, it might still be 'overkill' with the oil bath cam and relatively low pressure valve springs.
But I'd rather spend a little more on oil than on a new camshaft and lifters..

James

October 22nd, 2021, 09:12 PM

Ah yes, the Lucas is available here as well, but much more expensive. I know the Lucas should have a higher ZDDP content (I believe around 2000 PPM), this MPM stuff runs around 1200 PPM I believe. We'll see, it might still be 'overkill' with the oil bath cam and relatively low pressure valve springs.
But I'd rather spend a little more on oil than on a new camshaft and lifters..

You all now the saying "Pay a little now or pay a whole lot more later". With these engine lasting almost forever I would hate to tear it down due to the wrong oil being used.

Prowbar

October 24th, 2021, 11:40 AM

You all now the saying "Pay a little now or pay a whole lot more later". With these engine lasting almost forever I would hate to tear it down due to the wrong oil being used.

Yes sir. Take care of it and it will take care of you.

Prowbar

November 4th, 2021, 10:05 AM

Update:

Fitted the wiper and cowl. Remade one of the wiper shaft bearings as a piece had broken off. Made adapters for the wiper arms to facilitate the use of modern style wipers.

Added separate ground wires to the turn signals, these work now like they should. As a connection I used the caged nuts that are used for Chevrolet turn signals, but are not used on the GMC. These are 8-32 thread.

Took the fuel tank out to rustproof the double wall behind the cab and rear of floor, and to replace the plastic filler neck as it was cracked.

Most work is going into the preparations to build the bed back up. Paint work on the cross sills and bed strips, weld work on the fenders etc. Lost one cross sill in the fire, had to fully redo a repro piece of junk to get it fit properly.

Still working on the heater box, the heater core leaked, a solder repair should to the trick. It was full of calcium so that was cleaned out. If it does not work out I will order a new heater core.

Prowbar

November 22nd, 2021, 03:09 PM

She's coming along nicely.

Mentioned a solder repair would do the trick on the heater core... No sir. A local radiator shop soldered a new core on, which was about the same cost as purchasing a new one and having it shipped from the US. They did a nice job, which allowed me to put the heater back together, finally. Got the heater installed. Then the blower motor would only work at the highest speed. Replaced the blower motor resistor, works fine now.

Replaced the crusty heater hoses with new ones. I figured the elbow fitting on the coolant crossover was not original, so I took it out. Turns out it is original? Anyway, will probably add it at a later date.

AZKen helped me by sending new lock wafers to rebuild the original worn out locks. The package stayed about a month with the customs... I also had new keys made by a guy on Ebay. Very satisfied with the rebuilt locks, they work as they should now.

Finally started on the bed. Got the cross sills and new bedsides installed. Everything is looking good. Will have to square up the bed and do some rust repair on the wheel tubs. The tailgate will be installed soon also. Made a new wiring harness for the taillights, installed it also, with separate ground wires. I added the connectors in the harness as I'm not sure how I would have to install them otherwise, except for taking apart the taillight bezels with the pigtails. This modification is easier and user friendly.

The taillights did not work without a bypass ground wire to the cab, so I will install a separate ground wire from the bed to the chassis, and possibly from the cab to the chassis as well. I already suspected that ground would be an issue with the bed since I used pads from thin rubber between the chassis and cross sills to reduce noise and metal to metal contact.

The bed wood that I will be using is IPE. Very hard, durable hardwood that is usually used for flooring and decking. Read about it on a forum, others had success with it.

Prowbar

November 29th, 2021, 08:12 AM

Took her out for a test drive the first time. The brakes work well and have settled in quickly. First, it pulled to the left when stopping, which went away after a couple of tries. The engine did warm up nicely and the new heater works well. I'll remove the pan to repair the dent and change the oil next time.

The second gear synchro from the SM420 is pretty worn out, probably from its use on a farm. I've read that the 2nd gear synchro is integrated into the first gear. I hope to rebuild the transmission if I can find another unit to use temporarily. These pop up from time to time.

The speedometer or cable, or the drive in the gearbox still makes some noise when driving. Not sure where it comes from yet.

Picked up the Ipe wood for the bed floor. Don't have a picture, unfortunately. Assembling the bed floor will be the next task.

Prowbar

December 18th, 2021, 05:49 PM

Here you can see the IPE wood. Because of the width of the original bed planks, some still need to be glued together as they are not available in this width. I've matched the planks as to get a nice result. There are lots of variations in the IPE which should make for an interesting look.

However, for now, a temporary plywood floor will have to do.
To have it registered here it will need to pass an inspection first. This is planned on the 3rd of January of 2022, meaning pretty soon.

Due to covid I had to spend about a week at home in quarantine meaning I could not do as much as I had planned. No issues, just a cold basically.

Will have to finish the last details and it hopefully passes first try.

From then on I'll work on the proper bed floor, rust repairs etc. But the first priority will be the propane conversion. It still runs on regular gas now.

As a comparison: The cost of a gallon of gas is 8.08 USD here. (calculated)
Propane is less than half of that luckily.

FetchMeAPepsi

December 18th, 2021, 06:21 PM

Prowbar

December 18th, 2021, 06:48 PM

That wood is going to look great! Do you plan to coat it or anything or just leave it natural? A quick look online says it's naturally resistant to just about everything. It's a wonder that it ever rots in the forest, haha!

Thanks. Yes, I'll stain it with oil. If left natural, the wood turns to a light gray over time. Because it is so durable and hard it would definitely make sense to use it as a bed wood. Of course it will be protected when hauling stuff like engine blocks etc haha

Prowbar

January 5th, 2022, 05:47 PM

So... in the last few weeks, I finished the truck for inspection. The inspection was on Monday the 3rd, passed the first try. Right now I'm working on the license plates and the last insurance-related things. So hopefully by the end of the week, possibly next week I have the GMC on the road!

From then on I'll start to focus on the aesthetic side, for example, the bed floor and the V6 badges, and rust repairs. But propane conversion will be first and a gearbox swap.

The current SM420 is pretty clapped out. It whines to high heaven and the 2nd gear synchro is shot. Saturday I hope to pick up another 420 as a temporary gearbox while I rebuild the 'numbers matching' 420. The 420 I hope to pick up sat behind a plaid valve cover '63 305! Hoping to take a glance at those plaid valve covers too!

Prowbar

January 8th, 2022, 05:36 PM

Brought the SM420 home. This shifting pattern is much tighter, you get the impression that you're actually shifting instead of stirring in the soup... :upyes:

Took the shifter out and removed the top cover and inspection (PTO) cover. Drained the old fluid and cleaned the magnet on the bottom. All looks good, a much better tranny than the current one. Synchro's all look to be in good shape.

Hope to install this tranny soon. Should take care of the shifting issues. I think I'll keep this tranny installed. Rebuilding the other one might improve the synchros, but will cost a lot to rebuild and the shift forks are still worn, resulting in the sloppy shifting.

The guy I visited had a '63 305D. Those plaid covers are something else, arent they?

Prowbar

January 22nd, 2022, 07:41 PM

Installed the "new" SM420 today. Before installing I cleaned her up and painted her black. Also replaced the rear (yoke) oil seal, as the spring wore through the rubber.

When I pulled the shifter from the old tranny, it turned out that it had the later SM465 shifter! I know these interchange but the 465 is a 2 piece shift fork design to keep the vibrations to a minimum. Turns out the roll pin that secures the fork to the shifter was so loose it created the sloppy shifting.

Anyway, when removing the old tranny the bellhousing and yoke bolts were snug but not tight... :ahhhh:
When turning the transmission by hand you can hear the noisy ball bearings.

Anyway, out with the old and in with the new. I used the yoke and speedometer connection from the old tranny as the one on the 'new' tranny were for 4.56 or even lower. Also reused the old 'donut'. See photos. Cleaned the throwout bearing and greased her up, when through the whole clutch mechanism to properly clean and grease the moving points.

The new tranny shifts a whole lot better! The 2nd gear synchro works like it should and the tranny is tight.

However, when shifting from 3rd to 4th and the RPMs drop to 800 or so and you accelerate there is a strange noise... Above a certain rpm (about 1400 I guess) it is gone, no matter the load applied to the transmission.. the old tranny had the same thing, so it probably is not the tranny but I'm not sure what it is. It sounds like it comes from the tranny, not the rear axle or something like that. I'll try to record a video capturing the noise.

Have been cruising with the GMC some lately. According to my calculations, I'm getting 13.4 MPG. Was expecting worse so not bad. Been gathering parts for the propane conversion as that will be next, together with the IPE bedwood.

Would like to upgrade the exhaust though, at least switch the muffler. Right now it has the factory muffler which is quiet, a little too quiet. Hoping to find a muffler that is a little louder but lets you hear the V6 rumbling. Right now I can barely hear the engine in the cab. I still have the factory single exhaust and muffler. Any suggestions please let me know :thumbsup:

Prowbar

February 28th, 2022, 08:53 PM

Did a compression test today. All cylinders 125 psi! Took so long as I had to make an adapter because of the threads being so deep in these heads.

Did some fooling around with mufflers, had a turbo muffler on, an old Daytona made piece. I did not run a tailpipe, just the original muffler removed with couple the new one with an adapter. Liked the 'loudness' first but that goes away fast and the cab drone is annoying. Turns to obnoxious real fast IMO.

Will switch back to the OEM quiet muffler for now. Mine is still original and does a great job at keeping the noise low. A little more rumble would be welcome but that is it.

Planning to upgrade to 2.25 inch (true) duals. Looking at some mufflers now. Think I'll go with the Walker 17911 quiet flows. Should be quiet but still an upgrade over the factory single exhaust.

Changed the coolant.

Also working on the IPE bedwood. Propane conversion coming up soon..
Got most of the parts for the conversion gathered. Will keep you posted with pics when I get it installed.

Future plans:
HEI ignition from the Buick 231 V6
Toolbox in the bed for tools and general stuff. This also houses the propane tank.
Easy to use bed tie-down system to carry stuff around in the bed.
Improved PCV system that does away with the built-in cylinder head PCVs.
Headlight high beam and low beam via relays.
Rust repairs
Paint (503 light green with the white bumpers etc.)
Cosmetic upgrades
Replacing worn out and cracked parts like the front and vent window rubbers.
New towing bumper from my own design, copying the original but lighter, better made in regards to rust prevention etc.
Trailer hitch and wiring to complement it.

Prowbar

March 24th, 2022, 07:33 PM

Not much to add other than some small electrical issues solved. Still working on preparation for the bed wood and propane conversion. Pretty busy, not much time at the moment.

However, I did find out that my 305E has valve rotators, on both intake and exhaust valves! According to my 65 manual, these are optional on 305E's. Definitely a nice option to have!

Prowbar

April 27th, 2022, 09:19 PM

A month later! Had to do a lot of work on my other car ('89 Golf MK2 1.6 diesel, slow but very good mileage, around 50 MPG)

Almost finished the dual exhaust, decided it was time for a fun project. Got 'er done but still lacking the end pipes (behind rear tire). Will need some extra 90-degree bends for these. Picture will follow when that is finished.

A couple of small exhaust leaks will have to be addressed.

I used the Walker 18230 mufflers, with is a replacement muffler for Chargers and probably other B bodies with 426 Hemi and 440 engines I believe. Used 2.25" aluminized pipes. Nice and quiet but with a good rumble, meaning you can hear the engine well, especially when you step on it. Exactly what I wanted.

Also repaired the heat riser as it did not move freely. Got it to move freely. By testing on the bench with a heat gun it worked like a charm. Turns out it never opens when driving, probably from the wind cooling the heat riser. The bi-metal spring is 'worn out', opening at a temperature that is too high.

So I will probably delete it but will tie it open for now. Hate heaving to hear the engine running on 3 cylinders with those duals :(

Question: any forum members still have the heat riser on your 305 or did you delete it?

James

April 27th, 2022, 10:09 PM

Question: any forum members still have the heat riser on your 305 or did you delete it?

I wired it open once I got it open.

Prowbar

April 29th, 2022, 06:11 PM

I wired it open once I got it open.

No troubles with cold start/cold engine hesitation etc?

James

April 29th, 2022, 09:18 PM

No troubles with cold start/cold engine hesitation etc?

Not really. With the choke it run just fine.

Prowbar

May 9th, 2022, 09:57 PM

Here's a video of the dual exhaust rumble:

 To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

Edit: regarding the 'knock' you hear, I believe it is piston slap, it goes away quickly when the engine warms up some. Also wired the heat riser open, however will try to tighten up the bimetal spring to get it to work properly. Otherwise it will be deleted.

Finally took apart and cleaned up the rocker arms. They had a layer of sludge in them. Luckily all the parts were in good shape, seems they got lubrication from somewhere. All the oil passages are clear now.

A top tip for someone running one of these for the first time is to clean these out first!

Ed Snyder

May 9th, 2022, 11:35 PM

[QUOTE=Prowbar;75675]Here's a video of the dual exhaust rumble:

 To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

Your truck reminds me a lot of one I used to have -- another black 3/4 ton. It had a 351 in it.

Prowbar

May 10th, 2022, 07:42 AM

Ed Snyder

May 11th, 2022, 01:19 AM

[QUOTE=Ed Snyder;75676]

Yours is indeed very similar! Wish mine had the 351 though. The shifter in your truck had some odd bends to it?

I don't recall any odd bends in the shifter. I owned that truck about 20 years ago.

Prowbar

May 11th, 2022, 06:16 PM

[QUOTE=Prowbar;75678]

I don't recall any odd bends in the shifter. I owned that truck about 20 years ago.

The picture had me fooled, never mind.

Prowbar

June 4th, 2022, 06:43 PM

Here's a picture of the IPE bed mock-up. Finally started working on it, so far I'm 2 days in. A real learning experience, to be honest, I'm glad when the bed floor is done. Some of the square holes in the new bed strips are not located where they should be, meaning I will have to oblong the holes in the cross sills to get everything to fit... the glory of repro parts.

Luckily I can use the car lift, which saves me from having to crawl underneath every time to fasten the bolts.

I've treated the IPE board with 2 coats of hardwood oil, and more coats on the ends. The bed strip grooves were cut in the boards, and I added water gutters every 10 inches so the water can run out of the grooves. See picture.

The oil really makes the wood come alive, as you can see in the last picture. As you may have noticed I had to make the 7 7/16" and 6 3/8" boards out of 2 pieces, which and glued together with tongue and groove. I tried to match them as good as I could, and I really like the sheer difference there is in the wood texture and colors. Makes it come alive to me.

Hopefully, I can finish the bed floor next week. Then I'm going to start on the propane conversion.

If you want to create a bed floor that is long-lasting, and something that is different than plain oak, I would definitely recommend IPE. One thing though, if you're working with the wood, I recommend working outside or inside with proper ventilation. There's this yellow dust in the wood, it is nasty stuff.

Prowbar

June 8th, 2022, 07:38 AM

The bed wood is finished!
Having built the bed on the back of the truck, it made getting to some fasteners a little more difficult. For example the fasteners underneath the 3rd (wide) crossmember are blocked off by a chassis crossmember. To remedy this, I lifted up the bed using axle stands. This worked out fine and allowed me to fasten the bolts.

I'm glad that it is finished, and definitely worth the results.

Now onto the propane conversion..

But first I'll have to replace a leaking axle seal in the Dana 60. I reused the original seals, and one started leaking, unfortunately.

Also, the engine consumes some oil. Unfortunately, it started to get worse yesterday. Constant blue haze at idle from one cylinder bank... I believe it comes from the cylinder heads. That guy that I bought the transmission from has a good set of 305 heads. I hope to install these for the time being, and in the meanwhile, I can rebuild my own cylinder heads.

Bronze valve guides, hardened seats, positive valve seals, and some decking to increase the compression ratio is the plan, possibly with some light porting work to clean up the casting.

James

June 8th, 2022, 02:19 PM

But first I'll have to replace a leaking axle seal in the Dana 60. I reused the original seals, and one started leaking, unfortunately.

If the original seals was made of leather, as oppose to neoprene, and hard they can be softened up using saddle soap. If there a groove in the spindle it can be filled with Devcon Titanium epoxy and sanded smooth. This is what I had done to mine.

Here is a couple of location and not the only ones.

Saddle Soap: To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

Epoxy: To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic?

Prowbar

June 8th, 2022, 02:36 PM

If the original seals was made of leather, as oppose to neoprene, and hard they can be softened up using saddle soap. If there a groove in the spindle it can be filled with Devcon Titanium epoxy and sanded smooth. This is what I had done to mine.

Here is a couple of location and not the only ones.

Saddle Soap: To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

Epoxy: To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

Thanks for the reply James. The seals that were installed on mine were made of rubber, with a steel housing. There used to be a pretty severe groove on both spindles, but I repaired those with SKF Speedi Sleeves, as described in a previous post.

By the way, here is something for people that are wanting to build up a bed:
The 1/4'' bolts are secured in the cross sills with a washer, then a lock washer and a nut. When working from underneath it is a severe pain to fumble around with the two washers are also having to install a nut while keeping the bolt from coming out of the hole.

I made an adapter for the 7/16" socket that holds the lock washer and washer in place. Makes installing these much easier! See pictures.

Also, to keep the bolts from coming out of the bed strips when installing the nuts I used two cutoff pieces from the board to support the strip on one side. I can then reach around and support the bolt from underneath. See picture.
Of course this does not work for the last board, so you need a helper for the last one.

Prowbar

June 12th, 2022, 03:06 PM

I've created a picture album with some pictures of the truck when I bought it, and with some milestones regarding the progress.

Had a leaking axle seal. Turns out the seal lip was worn to a point where it barely had any pretension. The Speedi Sleeve looked very good. I did not feel like ordering a seal from Rockauto, so made an adapter to use a standard 2.375" oil seal (edit: wrong size given at first). This has a light press fit into the hub and it is secured with Blue Loctite.
See pictures.

To clean up the oily mess I'll boil the brake shoes to remove all the oil from the linings.

FetchMeAPepsi

June 12th, 2022, 03:23 PM

Do you have the part number for that oil ring?
I'd like to see the before and after on those brake shoes too.

Prowbar

June 12th, 2022, 06:39 PM

Do you have the part number for that oil ring?
I'd like to see the before and after on those brake shoes too.

The ring that houses the oil seal is one that I made myself on a lathe. I used a standard oil seal, 2 3/8" x 3 1/8" x 3/8"

Here is the one I ordered: To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

I took some pictures, the one before got a bit blurry. Before boiling I removed most grease and grime from the shoes.

The after shows the linings after they were boiled in a mix of water and washing soda. After boiling I cleaned them with some brake cleaner and a rag.

In my opinion, this is a great way to 'rescue' brake shoes, after they have been soaked in brake fluid because of a leaky wheel cylinder or a leaking axle seal.

David R Leifheit

June 13th, 2022, 05:54 PM

Working on the frame paintjob. Already did the rear of the frame while it was on the ground, now doing the frame rails underneath.

I'm using this product for the first layer: To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

Basically a product that penetrates the surface rust on the frame. This seals off the rust. It is applied with a very light coat. luckily the frame had very little loose rust that had to be brushed off first, so this saved a ton of time.

When this coat is fully completed, I can move on to the final paint. This is a black chassis/frame paint from Monopol. It is a 2 part deal, based on epoxy.

Some places of the frame I cannot reach right now, because other parts are in the way. These will be done later, whenever the cab is lifted off. I will do what I can, which is the frame and crossmembers, parts of the radiator support etc.

To project the several grease fittings on the front suspension and driveshaft from dirt and dust, these are small cups available for them. To try these out I have fitted them on the grease fittings. We'll see how it works out in the long run.

Also discovered that the oil pan and bellhousing recieved a nice dent, luckily no rubbing from the flywheel. See picture.

My experiences are that many oil pans look like that. I think I sold/traded off all my spare undented ones (and a few with minor dents). The flywheel cover is a nice item to have, although I don't think any of my trucks actually still have theirs. I might have one or two in the barn or garage that I intended to put on a truck ... eventually.

*I say eventually since I have a '63 305 V6 that has the Holley conversion and Electronics, along with the Scotsman plaid covers that has been waiting to go in my '63 for at least 10 years now. Sitting right next to the wife's motorcycle that has been on the motorcycle lift for about the same amount of time (and I have not heard the end of that! Every summer... )

Prowbar

June 13th, 2022, 09:27 PM

My experiences are that many oil pans look like that. I think I sold/traded off all my spare undented ones (and a few with minor dents). The flywheel cover is a nice item to have, although I don't think any of my trucks actually still have theirs. I might have one or two in the barn or garage that I intended to put on a truck ... eventually.

*I say eventually since I have a '63 305 V6 that has the Holley conversion and Electronics, along with the Scotsman plaid covers that has been waiting to go in my '63 for at least 10 years now. Sitting right next to the wife's motorcycle that has been on the motorcycle lift for about the same amount of time (and I have not heard the end of that! Every summer... )

Back to work! :banghead:

Prowbar

June 14th, 2022, 05:35 PM

Good news! Filled 'er up with expensive gasoline (98 octane unleaded), added lead additive, and got 14.7 MPG! Pretty satisfied, and that is just "normal driving" for me.

Bone stock (as far as I know) 305E with the 2 barrel Stromberg and original points ignition. SM420 transmission, 4.10 Dana 60 and 31 inch tires.

Gas prices, converted for 98 unleaded, is 10.10 USD per gallon. Need to get the propane installed!

David R Leifheit

June 14th, 2022, 07:44 PM

Back to work! :banghead:

That is my problem. Work.
When I got infected with the GMC bug, I was out on disability.
All the time in the world, no money.
Now that I have found a good job I can do its almost the opposite.
I have money, just no time.
:)

Prowbar

June 14th, 2022, 09:45 PM

That is my problem. Work.
When I got infected with the GMC bug, I was out on disability.
All the time in the world, no money.
Now that I have found a good job I can do its almost the opposite.
I have money, just no time.
:)

Sorry to hear.

lizziemeister'sV6

June 14th, 2022, 10:57 PM

Work to live - not live to work.

Prowbar

July 6th, 2022, 07:05 PM

Ok. Now that I got that 478 I have to focus on getting the propane conversion done first - in order to cut my fuel costs by more than half :teehee:

I wanted to wait with the conversion because I wanted to get the bed floor in first, which is installed now.

This tank has a 200L capacity, which is around 52 gallons. However, because of safety reasons ie. expansion of the propane as it heats up in the sun, the tank will be only filled to 80% capacity. That leaves 160L or 42 gallons of propane capacity.

I chose a round tank mounted on the bed. I did this to get some genuine capacity. There are tanks that go in place of the spare tire, but these have a much smaller capacity and are much more expensive. I offset the tank to one side, so I can put stuff on the other side whenever I built a toolbox around it, which is a future plan.

In order to mount the propane tank, it has to be attached with brackets to the frame. As it is one heavy SOB when filled up I made a frame that houses the brackets and bolts to the 2 front frame mounting points for the bed. It is now solid as a rock.

Next, I'm going to connect the filler hose and filler opening - and I have a nice trick up my sleeve to hide the filler opening, which you shall see.

A tank meter is not yet installed on the tank. There is the possibility to have a gauge in the cab, however, I will just meter from the tank itself.

Also connected to the tank will be the liquid propane line that goes to the converter in the front. This line is about the same size as a regular 1/4" brake hard line. Remember, it is fed under a pressure of 8 bar (116 psi) to the converter. Also connected to the tank is a wire that operates the solenoid to enable and cut off the propane supply to the line.

The converter converts the liquid gas to a gaseous state. The converter is kept from freezing by the (hot) coolant from the engine. I will place my converter on the return line of the heater.

From the converter, the gaseous propane is fed to the 300A mixer, which is mounted on top of the carburetor. When driving on propane the gasoline supply is cut off and only the throttle blades of the carburetor are used. This IMPCO mixer allows for driving on propane as well as gasoline.

In order to keep the gasoline system working, I'm switching to an electric fuel pump. I can flip a hidden switch in the cab to switch from gas to propane use or vice versa. I will be using a second choke cable to operate the IMPCO 300A mixer. All this will be explained later.

Prowbar

August 10th, 2022, 08:25 PM

Another piece of the puzzle is completed regarding the liquid propane conversion.

I added the filler hose and filler attachment which are hidden behind the license plate. It runs to the tank.

From the tank, a copper line is run to supply the converter. It first has to pass through a valve, which combined with the solenoid on the tank, turns on or shuts off the propane supply. The gas supply is controlled by the electric fuel pump and electric gas shut off valve.

I've also almost completed the wiring harness for the pumps and solenoids. The wiring has a relay that is enabled when the engine is turning. This is done via an induction pulse from the coil. With a switch under the dash I can change between gasoline and propane fuel.

I've added a second choke cable to operate the mixer on top of the carburetor to switch between gas and propane. This has to be hooked up.

Top tip: the 60-63 repro choke cable is a deluxe cable with a chrome bezel. Removing the bezel doesn't give you a standard choke cable with the serrations... Unfortunately.

In this conversion, I try not to modify the existing parts. I also use whenever possible, existing holes to mount parts onto. This way these modifications can easily be reversed and it keeps everything original, which I like.

All that is left to do now is to hook up the choke cable, complete the wiring and install the mixer with air cleaner. Then my fuel mileage triples (well the cost of fuel decreases that much :))

Last thing: notice those V6 badges on there!!! Finally had them painted and they pop! Now the whole world can know there is a big block V6 in my truck

Prowbar

August 14th, 2022, 07:23 PM

Propane conversion is, except for a few brackets and final touches, finished! I've made a little video that shows the GMC running on both gasoline and propane. Hopefully this will make it clear. Took it for a cruise today, has good power. Next thing to do will be to visit someone that has a good exhaust gas tester, to tweak the mixer settings for the proper mixture and emissions.

 To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic?

Ed Snyder

August 14th, 2022, 11:14 PM

Propane conversion is, except for a few brackets and final touches, finished!

By way of comparison, I thought you might like to see photos of another propane installation. This '63 GMC was owned by the regional natural gas company, and had been converted to propane when it was new. So it never ran on gasoline.

Prowbar

August 15th, 2022, 08:24 PM

By way of comparison, I thought you might like to see photos of another propane installation. This '63 GMC was owned by the regional natural gas company, and had been converted to propane when it was new. So it never ran on gasoline.

That is neat! And they kept it as simple as possible. Looks like they removed the WW carb and installed a carb for gaseous fuels on there. Interesting to see the converter and fuel switch on the other side. As you said, only natural gas. Did they keep the fuel tank in? And the fuel pump was removed? Cannot see that in the pictures.

The installation looks clean, and that is my goal also. I have the big oil bath air cleaner from the 478, when I get the 478 in I'll see if I can 'gut' the air cleaner and 'hide' the air filter and mixer in there. Should look a lot nicer.

Ed Snyder

August 16th, 2022, 12:01 AM

That is neat! And they kept it as simple as possible. Looks like they removed the WW carb and installed a carb for gaseous fuels on there. Interesting to see the converter and fuel switch on the other side. As you said, only natural gas. Did they keep the fuel tank in? And the fuel pump was removed? Cannot see that in the pictures.

I took those photos 21 years ago when I was trying to buy the truck. The owner wouldn't sell, though. The fuel tank was still behind the seat, but there was no filler cap on it. I think the fuel pump port was blanked off.

It was a cool truck -- short wheelbase half ton with a utility box on the back and the rare big back window. Hardly any rust or dents either. Odo showed about 90K miles.

Prowbar

August 25th, 2022, 04:36 PM

A couple of things got finished today. First of all, I bought a Buick V6 HEI to use. I used the 478 distributor for the gear, and installed this on the HEI. The 478 distributor is pretty outdated because is has no vacuum advance. But it does have the uniset points, which is a neat system.

I followed Peter Chronis' method by welding up the shaft and turning it, then drilling a new hole. Akin to the original I re-riveted the gear on the shaft.

From a piece of aluminum I made the bushing myself. I made new plug wires from a generic V8 set. I set plug gaps to .045" to start.

I had already reserved a 12 volt wire from the ignition to use for the HEI. The ignition pulse for the propane is retrieved from the tachometer port on the HEI.

Installation is pretty tight but once it is in, it is fine. The first startup it idled immediately, which is awesome. I set initial timing to 12 degrees. My engine seems to like more initial to idle properly. I have ported vacuum advance, maybe that is why.

The second modification is my conversion of the stock PCV system. I don't like tapping into 4 of the 6 ports, so I removed the valves and capped them off with 1/4" NPT plugs. I then converted a push in valve cover breather to use a oil filler cap connection. A random Gates PCV hose I found online fits perfectly and redirects the blowby gases to the IMPCO mixer PCV port.

HEI, propane and the PCV conversion should clean up emissions significantly. Tomorrow I'll have it hooked up the exhaust gas tester and I'll see if I can share the final results.

Prowbar

August 26th, 2022, 08:16 PM

Using the exhaust gas meter we adjusted the emissions today. Before it was almost 6% CO (carbon monoxide) at idle which is extremely high. However, with propane, you don't really notice the excessive hydrocarbon smell (at least outside). Readjusted the idle and checked the emissions at 2500 rpm which was fine.

We set a goal for about 1% CO at idle, which is still a little rich for propane but makes cold starts easier. With the dual exhaust on the left-right values differ a bit but nothing to worry about. The mixer is really sensitive to changes and when we got close we left it as is.

Overall very happy with the other values such as the unburned HC which are really low for an old engine like this. I think this is due to the HEI + PCV conversion. Out of curiosity, I might revert to the stock PCV and spark plug gap and then recheck. Should have done this when the points were still installed but oh well. I have a feeling the stock PCV system will produce more unburned HC's.

Prowbar

October 15th, 2022, 08:58 PM

Had the chance to test the GMC on a chassis dyno today.

Did two pulls:
1. Propane. 123.7 net HP (DIN norm) at 3500. 296 Nm (219 ft lbs) at 2380 rpm.
2. Gasoline. 145.5 net HP (DIN norm) at 3990. 312 Nm (230 ft lbs) at 2480 rpm.

This is a good running but worn 305E with 125 psi in all cylinders, a very worn timing chain, a 2.25-inch true dual exhaust, HEI ignition, and the stock Stromberg WW carburetor.
SM420 transmission, 4.10 geared Dana 60 on 235/85R16 tires.

As you can see, the torque curve is fairly flat, with torque peak at 2400-2500 rpm compared to the factory's 1600 rpm. We tested to around 4000 rpm.
It also lacks some torque compared to Jolly's chart.

I am assuming the 305E that is in this truck is a fairly worn engine, abused throughout the years. Combined with the wide ratio SM420 it isn't a fast truck by any stretch of the imagination. I don't mean to race the thing either but I do like some power :)

The power losses with running propane are definitely noticeable and this can be seen in the results.

I intend to gain a lot more power with the 478, and then I'm planning to repeat the chassis dyno test. very curious to see how it will perform.

Prowbar

January 21st, 2023, 06:30 PM

Time to pull out the leaky 305 to install the 478. Need to borrow some parts from the 305 first. Also, finish the frame paint in the engine bay and paint the firewall in the 503 light green color. Started today by pulling the SM420, then took it apart to change the front seal (I had changed the rear seal prior) and chamfer the ends of the shift forks to allow for a cushion of oil to be forced in between the fork and shift ring. All looks good and new oil will be added when the trans is installed.

Now onto pulling the old 305, then freshening up the engine bay. Got quite a few jobs to do. Been looking to get started for a long time, quite the feeling when you get there :upyes:

Prowbar

January 28th, 2023, 06:37 PM

Ok, pulled out the 305 today. Loosened all the bolts, connectors etc. Everything came out easily. Pulled the engine and the original mounts were pretty stuck to the frame, so the rubber separated from the steel plate. No big deal but a shame nonetheless. I have new mounts though, thanks to Musicman70 from 67-72 Chevy forum (Funky61is that you?) There was a thread from a guy rebuilding a 305 and it was hinted that these motor mounts from Anchor (2337) would work, and 2107 and 2108 for the transmission mounts.

Lifting the engine took more work than expected because the engine hoist couldn't lift the engine high enough, so we had to use a crane on the ceiling to lift the engine higher. In the end, I have the 305 sitting on wood blocks, waiting to donate its parts for its bigger brother.

In the last picture, you can see a possible oil leak that I did not discover before: either from the distributor or from the camshaft galley. There is a freeze plug in the camshaft hole but not the block-off plate as is on my 478.

Now onto cleaning the engine bay, then painting it. Then start transferring parts from the 305 to the 478.

Funky61

January 28th, 2023, 11:04 PM

Musicman70 from 67-72 Chevy forum (Funky61is that you?)

Yes, one in the same Prowbar.

Great work and thanks for posting your progress. :welldone:

Prowbar

February 12th, 2023, 02:11 PM

FetchMeAPepsi

February 12th, 2023, 03:11 PM

Went ahead and stripped the complete front end to prepare for paint. Will do the front suspension and steering at a later date. Don't want to keep the truck off the road for too long, or I'll start to miss driving it :)

Just been busy cleaning up all the parts, removing almost 60 years' worth of caked on grease.

That grease removal was one of my least favorite parts. I bought a 5 gallon bucket of Super Clean (purple stuff) and it helped a lot. Still wasn't fun though.

You're making some great progress. How cold is it where you are right now?

Prowbar

February 12th, 2023, 05:25 PM

That grease removal was one of my least favorite parts. I bought a 5 gallon bucket of Super Clean (purple stuff) and it helped a lot. Still wasn't fun though.

You're making some great progress. How cold is it where you are right now?

Thanks Fetch. the weather varies between 40 and 50 degrees Fahrenheit right now (converted it for you guys :))

For grease removal I use a product called Elbow Grease :D The best way I've found is a trip to the local car wash to spray the 'wet junk' off and then use an old flat-bladed screwdriver and a putty knife to scrape off the thick, dry layers. It is so caked on that no solvent really penetrates it. A variety of brass, steel and nylon brushes are used also. For the last bits and to clean the surface I use my parts washer with a degreaser. To prep for paint a silicone remover fully cleans the surface.

Parts such as the bell housing takes a couple of hours to fully clean, but in the end, it's all worth it.

Forgot to mention, but the previous owners in the USA must have driven over a very hot asphalt road as there is a nice thick layer of asphalt in the fenders, covering up all the bolts. Fun stuff to find them and get them all loose. No rust or stubborn bolts, nowhere. That is a blessing.

The only rust spots I have to fix are the typical front fender reinforcements, a small hole in the floor, and a spot in the radiator support because of a leaking battery.

lizziemeister'sV6

February 12th, 2023, 05:46 PM

Prowbar

February 12th, 2023, 06:11 PM

Could be that the tar coating you're talking about was applied as undercoating when the truck was new. A good idea that worked well until the coating aged and cracked then allowed road grime to get under it and cause rust. We have all experienced the outcome of salt/dirt that found pockets and seams to rest in over the years - some of us more in the "Rust Belt" compared to the sunny southern states.

Pretty sure it is asphalt. I added a picture. Some layers are 3/4" thick. There's still lots of OEM undercoating on this truck, which is a very thin gray layer. It flakes off now. I have also found the original GM rustproofing in the doors. It also comes off in big chunks.

Anyway, this is a CA built truck and it had a Washington title on it when I bought it. It must have spent most of its life in very dry conditions as there is only very light surface rust on everything, except the usual rot in the fenders, rockers, doors, hood cab corners, windshield etc.

The picture is a shot of the right fender reinforcement, behind the front wheel. It has some damage and a piece of tin can along with lots of Bondo was used to 'fix' it.

Prowbar

February 23rd, 2023, 01:13 PM

Busy on the front-end work. Originally I wanted to paint the truck in the 503 light green/turquoise color, but decided against it. There is still a lot of good original Flame Red paint left, and I've decided to bring the original color back as best as I can.

Right now I'm working on removing the layers of spray paint to reveal it. It is a tedious process, to say the least, but we're getting there. I'm using green ScotchBrite and nylon Dremel brushes to remove the paint.

I've cleaned up and painted the frame rails and part of the front end. These areas will not be easily accessible again when the 478 is in. The front end needs a total rebuild anyway, which is for a later stage. I could do it all at once, which is preferable from a restoration standpoint, but again I don't want to have it off the road for too long.

Once the firewall is completed, I can get back to the engine work and complete it. The engine can then be dropped back in.

I'm also working on rebuilding the starter motor and engine wiring harness. The engine harness was a fire hazard in the making. It will be redone with new cables while re-using the old connectors.

Prowbar

March 2nd, 2023, 07:48 AM

Working away on the truck. Most of the firewall paint was removed. A caramel disc (usually used to remove stickers) is an effective method to remove old spray paint. A couple of spots need to be touched up to finalize the firewall.

I rebuilt the starter motor with a new Bendix, brushes, and bearings.

478 has the timing cover and top end installed. Need to make a slight dent in the 305 oil pan to clear for the governor; the 478 oil pan is deeper. Can't run the 478 pan due to the slope in the pan interfering with the front end.

Also, I wanted to run the original 4-groove pulley due to the external weight. Turns out I cannot, it hits the water pump pulley on the light-duty timing cover. Planning to make a fixture to balance the 305 pulley to the 478 pulley; I will make up an external weight, which can be easily bolted to the 305 pulley.

Also working on the engine wiring harness. Hope to install the 478 soon, when the firewall work is completed.

For reference I took a picture of the crank shaft keyway. It has a very odd shape to it, basically an extended Woodruff key.

Prowbar

April 9th, 2023, 01:08 PM

Completed the firewall paint strip. Wanted to touch up spots first but decided to re-paint as a whole. Primer was next, it also serves as the conversion layer between the old and new paint. New 2K epoxy paint was mixed in the correct color, using an old panel as a reference. The firewall was then painted Flame Red, the original color of the truck.

Now the 478 can be installed (finally!!)

Did a lot of preparation work also. for example, the throttle and clutch linkage are all steel-on-steel. All of the linkages and holes showed excessive wear. I welded up the worn parts and filed or turned them to original size. Bronze bushings were made up, the old holes bored out and the bushings are pressed in and further secured with Loctite. The throttle linkage is shown as an example here. I also added a washer on the clutch linkage rod, as it did not have a good surface for the axial reaction forces.

Parts such as the timing indicator on the front pulley and other small parts are sent off for zinc plating.

There is also a picture of the balancing fixture for the front pulley.

Lizziemeister made a good comment about the undercoating last time. I check other trucks and indeed, what you can see on the firewall is the original undercoating. However, some spots are so thick, I figured it to be asphalt. How thick is the undercoating on your trucks? In the nooks and crannies of the front fenders.

Prowbar

April 9th, 2023, 01:17 PM

Originally I had planned to also paint the front inner fenders and radiator support etc. That will have to wait for another time, as there is a car show coming up that I would like to attend, and the weather is getting better by the day. I'm getting the urge to drive it again. Have to keep the big jobs in sections to avoid having it off the road for too long.

Rust repairs are the next job when this is finished.

Anyway, the second post is to show off the added ported vacuum advance port.
Originally this engine had no ported vacuum advance port, and I prefer ported over full manifold vacuum for drivability. Therefore a small aluminum block was made with a hose fitting. A small hole was drilled in the carburetor to allow for ported vacuum.

I could have gone with the Holley 500 CFM 2 barrel, but the engine will be running on propane most of the time so there is no benefit from it really. Also, the Holley throttle blades are the same size as the Stromberg WWC, so I doubt it will be inferior in airflow.

Prowbar

April 10th, 2023, 06:24 PM

Installed the 478 today. Took the engine off the stand with the engine hoist, then installed the bell housing, flywheel, pressure plate, clutch, starter, engine wiring harness. Checked the bell housing runout, .003". Pilot bearing runout is less than .002". Used the same method of removing the rocker assemblies and using a head bolt with a piece of strip as a mount for the chain.
Very satisfied with the install. Then installed the transmission.
Had to take the SM420 top cover off to clear the firewall.
Used new motor mounts (Thanks for the Anchor part numbers, Funky61)

After installation, we pulled the engine as much forward as we could to give the right side exhaust manifold as much clearance as possible. There is about 7/16" clearance between the manifold and firewall now.

Now, onto reinstalling the rest...

Prowbar

April 22nd, 2023, 06:07 PM

Been busy, but slowly building up the engine and hooking up everything.
Got most of the to-do list taken care of.
Hope to fire her up for the first time next week. I'll be sure to take a video.
We'll hook a manometer to the oil pressure sender, prime the engine beforehand, and then do a few rotations with the starter without the sparkplugs installed. Then add some gas to the carb and fire her up. Probably take her to 1000 RPM or so for 10 minutes and verify the lifters are rotating.

The carb fuel line is a temporary addition. It came with the carb and is easy for testing.

Prowbar

April 30th, 2023, 05:42 PM

What was supposed to be an easy start-up didn't turn out to be one. When we went to start the engine we quickly had coolant between the block and heads. Had some problems with poor starter performance as well. After a lot of attempts without any success, we gave up and drained the oil. Full of coolant...

Then made the decision to take off the heads. This went rather easily and soon was discovered that the coolant passages in the block do not line up with the head gasket. See pictures. This NOS head gasket (picture 5) only relies on crush rings to do the sealing. I never noticed this misalignment during assembly. This probably caused the leakage.
Also discovered that the cylinder crush rings seat inside the bore. Which is bad for detonation and gasket life.

Anyway, I have some Fel-pro 305/351 V6 head gaskets. They rely on gasket material instead of crush rings to provide the seal on the coolant passages. Fel-pro also turned these coolant passages into slots, which do line up, which is great. Even if they did not completely cover the bore, the gasket material would take care of the sealing. Now the bores still need to be opened up. I have tested one and it can be done, by moving the crush ring to a larger diameter. Now to make some specialized tooling to facilitate the process...

I was given the original GMC 478 head gaskets (that came off the engine, picture 3) as well. They line up properly. Which got me thinking... Maybe I've been given NOS 401 V6 head gaskets... which would explain the crush rings sticking into the bores...
And for the coolant passages, they probably moved them away from the bores to deal with the larger 478 bores... But this is speculation.

I'm glad we discovered it now instead of later... But it makes you feel like an idiot for not noticing.

Prowbar

April 30th, 2023, 05:46 PM

Picture of the 401 gasket (bottom) compared to the original 478 gasket (top). Notice the bore difference and the offset in coolant passages. What do you think?

Prowbar

May 5th, 2023, 06:35 PM

As talked about I made some tools to help form the gaskets from the 305/351 size to the 478. First off a plate with the locating dowels is made. In the center of each bore a hole is milled to hold a steel cup, which fits a bearing. This is the center is my bead roller setup.

The process starts by grinding down the old crush ring until they can be separated. This also separates the gasket. One bore is formed at a time, to keep the pieces properly located.

Then with a Dremel, the blue gasket layer is enlarged to 5.125" + some extra. A piece of plastic is stuck between the steel backing and blue gasket material to protect the steel backing from being cut.

Then with the roller and forming dies, the sheet metal backing is brought upwards and a new ring is formed. The length is then ground down to the right height and deburred. Then it is rolled over, forming a new crush ring. The sheet metal works easily and takes the shape well. The crush rings look good and smooth.

See the last picture for the finished modified gasket.

One head has already been installed with a new gasket. I also used some head gasket sealer as an added measure. So far it looks good. Tomorrow planning to reassemble the engine, then hopefully a first start without any troubles. I will be running straight water for the first start (without any calcium).

Of course, this is an experiment, maybe they blow out quickly, maybe not. We'll see. Some redneck engineering at its finest :ahhhh:

Prowbar

May 6th, 2023, 06:02 PM

Got this far today.

Prowbar

May 13th, 2023, 04:13 PM

To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

First start of the 478 V6!

Prowbar

May 14th, 2023, 12:38 PM

Here is a video of the second run: To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

Runs much better, throttle at idle wasn't opened far enough and we retarded the time some. Two of the valve lifters are spinning slowly, and two aren't spinning at all, these will be replaced with new Melling lifters from Rockauto.
For the experiment, I switched two lifters around, a fast and slow turning lifter, and the lifter is at fault, with no proper crown. These are the OEM lifters.

Lifters are easy to change, back off the valve lash adjustment, remove the pushrod and use a stick magnet to retrieve the lifter.

The 305 starter doesn't have the oomph and drains the battery rather quickly, have to figure out what causes it.

The haze from the manifolds is the paint baking.

Prowbar

May 20th, 2023, 09:41 PM

Bought me some new Melling lifters from Rockauto to replace the slow-turning or stationary lifters. After replacing them with the Melling lifters nothing happens at all.

Pretty ticked off. Makes me wonder if the cam is still decent. I measured the lobe lift before assembly and all intake/exhaust lobes had about equal height, but I couldn't detect any noticeable taper then. Might have to pull the cam, and have it reground, along with the lifters... Not the news I was waiting for, to say the least :pullinghairout:

I am using oil with proper ZDDP content.

Prowbar

May 26th, 2023, 08:21 PM

Going to pull the camshaft out and have it reground according to Bigblock V6 (Pete) specs. Also, new lifters.

Need to wait a bit before I can get the cam ground, but in the meanwhile, I can finish most of the tasks that still need doing:

Remove the camshaft
Exhaust downpipes welding. Bought an air-fuel meter to install.
Propane mixer adapter
New battery cables
Leaking rear axle seal
All sorts of odd jobs that need to be done

Keeps one busy.

Traced the slow starting to the starter itself. Have to look it over. Seems like the new brushes aren't seating properly. When the switched them for the old brushes, it cranked over just fine.

Prowbar

June 5th, 2023, 06:33 PM

Did a couple of things last weeks:

1. Made some better battery cables. The old ones were junk and made out of old welding wire and battery terminals we had laying around. One of the reasons for poor starter performance. Bought some 50 mm2 wire (equal to 1 AWG) cable with fine strands, very flexible stuff. Proper fitting battery terminals were soldered in and heavy-duty connectors were crimped and soldered. Heat shrink with glue protects from moisture and corrosion. I've added an accessory wire to the positive cable to supply the new relay-operated headlights with direct battery voltage. A connector will be added to easily connect/disconnect them in case of repairs.
The engine turns over much better now.

2. There is a picture of the added bronze bushings to the clutch pedal. I've mentioned this before but did not show a picture. As you can see a washer welded on the lower clutch rod. This prevents the clutch linkage from wearing in to the corner of the rod. The clutch linkage was made from hardened material, and couldn't use a regular drill, endmill, or reamer to cut the material. However, a carbide burr and some patience made a nice 1/2" hole, and the made up bronze bushings were pressed in with LocTite.

3. Made a new adapter for the Impco mixer to go on top of the carburetor. Hood clearance is minimal but present due to the higher raised manifold on the earlier 478s.

4. Welded up one of the downpipes, in this case, the right side. Still need to weld in the O2 sensor bung.

5. Started tearing apart the engine to remove the camshaft. Been studying the original grind and seeing how one could extract a little better performance from one. I've considered Pete Chronis' grind, but it is more of a higher RPM camshaft. Another issue is the lack of CNC camshaft grinders - all of the companies use a copy camshaft machine with existing cam profiles to regrind camshafts.

Some thoughts:
All durations are based on advertised numbers since this is what the GMC book gives.

- Stock cam LSA (Lobe Separation Angle) is 110 degrees. I would have liked to go lower, for example, 108 or 106, to improve low-end torque. However, not possible without welding up the cam I would think. Still open for discussion. Pete's specs keep a 110 LSA as well.

- Keep the stock 63-degree overlap between intake and exhaust. Pete's cam has a 32.6 crank degree overlap, which is much less. I believe the book also gives all cam duration in crank degrees since advertised duration numbers comparable.
- Stock intake closes 61 degrees after BDC. I would like to close the intake earlier, for example, 50 degrees ABDC for an increased dynamic compression ratio. Since the static compression ratio is low as is, one could extract a little more compression out of one. However, cylinder filling might become a problem. Pete's cam closes intake 46 ABDC, which is even earlier.

-A bit more cam lift would be nice to compensate for later intake closure. Still need to measure the stock camshaft lift.

-Keep the same intake duration of 268 degrees, if possible. However, reduce exhaust duration from 298 degrees to about 275-280 degrees.
Pete's cam has an intake duration of 236 degrees and an exhaust duration of 268 degrees.

Seems like Pete's cam really 'sacrifices' on intake filling by closing the valve early, having less intake duration, and less valve overlap.

Your thoughts on the camshaft?

Prowbar

June 5th, 2023, 06:42 PM

As mentioned, I also converted the headlights to relay. I was given a universal relay conversion kit for headlights. I made my own harness, with the original colors. The box has relays and also 2 30 amp fuses to protect the circuit. It is nicely hidden.

Had to cut off the original connector from the OEM harness to supply the relay box. Not pictured, but I've also added the original clips to fix the harness to the grill. Power is supplied by the battery cable accessory wire.

This should take a huge load off of the headlight switch and the rest of the wiring while improving the headlights' brightness as well. From a fire hazard in the making to a win-win situation.

Prowbar

June 10th, 2023, 08:24 PM

Been working on a cam design.

I've added Pete Chronis custom cam specs. Note these specs close the intake much later, to up the dynamic compression ratio. Note the shorter duration figures (advertised) These specs also have a little improved lift.

Stock lift figures as measured by me, with the current camshaft, without any valve lash, are .415" for both intake and exhaust.

I also added the cam I want to have ground for my build. I have to decide on the lift, but the rest is pretty much final. Unless you have groundbreaking suggestions :)

It is a compromise between the stock camshaft and Pete's design.

Compared to stock, earlier valve intake closing to improve dynamic compression. A little less duration as a result. The exhaust is about the same as stock. I was concerned with cylinder filling at first, but don't think it matters as much due to the improved valve job and slight porting in the heads.

I've also decreased the valve overlap compared to stock, but not as much as Pete's design. The lobe separation angle comes out to 109 vs the stock cams 110.

Let me know what you think.

James

June 10th, 2023, 08:51 PM

I have done some flow testing on a stock magnum head (reference the link). I didn't show it on the graph but the head continue to flow more air when there is more lift.
 To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

Also I have measure the maximum lift for both valves (reference the link).
 To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

Hope this will help in your planning on the cam lift profile.

Prowbar

June 10th, 2023, 09:22 PM

Thanks, James. Forgot about those posts. Good job on the data.
Your cam lift measures a lot more than mine, didn't think mine was all that worn. Not sure now, maybe the cam lift was revised a couple of times. Have to measure my 305 now also to compare.

Seems like more lift definitely helps.
Will talk with the cam grinder about how much I can safely improve the lift.
More seems better but I would have to probably change/modify the valve springs also.

The stock ones are lousy on seat pressure, maybe 50 pounds, maybe shim them for improved pressure or change them for another spring.
They are good are break-in springs, though.

I left the stock exhaust duration as is, the exhaust port on non-Magnum heads is pretty restricted, not much can be done about it I think.

James

June 11th, 2023, 05:12 PM

The stock ones are lousy on seat pressure, maybe 50 pounds, maybe shim them for improved pressure or change them for another spring.
They are good are break-in springs, though.

Personally I would installed bronze valve guide sleeves first. Then I will be using valve springs from Comp Cams #972. I will also need to use spring seat cups Comp Cams #4704, guide will need to be machine to allow installation. While you are getting it machine I would also get machine for positive valve stem seals. And to top it off with Comp Cams retainers #743. The springs comes extremely close to the stock seat pressure base on the maintenance manual specs, I also double check a set just to be sure. The springs are good for .700" before coil bind.

Here is something I found on Motor Trend web site:
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Lobe Displacement Angle (LDA):
Although the installer can advance and retard the lobe centerlines, the displacement angle between the centerlines is ground into the cam at the time of manufacture and cannot be changed by the end-user. Narrow LDAs tend to increase midrange torque and result in faster revving engines, while wide LDAs result in wider power bands and more peak power at the price of somewhat lazier initial response.
A street engine with a wide LDA has higher vacuum and a smoother idle. On the street, LDA should be tailored to the induction system in use. According to Comp Cams, typical carbureted, dual-plane manifold applications like 110-112 LDAs, while fuel-injected combos want slightly wider 112- to 114-degree LDAs. Fuel-injection doesn’t require the signal during overlap that carburetors need to provide correct fuel atomization, and most computer controllers require the additional idle vacuum that results from decreased overlap.
Bracket racers with higher stall-speed converters, high compression, single-plane intakes, and large carbs usually want 106-110-degree LDAs.
Engines equipped with blowers or turbos, or used primarily with nitrous oxide, typically work best with wider 110- to 116-degree separations. Race engine speeds have increased over the years causing a corresponding upward creep in LDA and duration

Duration:
Duration has a marked effect on a cam’s power band and driveability. Higher durations increase the top-end at the expense of the low-end. A cam’s “advertised duration” has been a popular sales tool, but to compare two different cams using these numbers is dicey because there’s no set tappet rise for measuring advertised duration. Measuring duration at 0.050-inch tappet lift has become standard with most high-performance cams. Most engine builders feel that 0.050 duration is closely related to the rpm range where the engine makes its best power. Typical daily driven, under-10.25:1-compression ratio street machines with standard-size carbs, aftermarket intakes, headers, and recurved ignitions, like cams with 0.050-inch durations in the 215- to 230-degree range if using a hydraulic grind, or 230- to 240 degrees with a solid.
When comparing two different cams, if both profiles rate the advertised duration at the same lift, the cam with the shorter advertised duration in comparison to the 0.050 duration has more aggressive ramp. Providing it maintains stable valve motion, the aggressive profile yields better vacuum, increased responsiveness, a broader torque range, and other driveability improvements because it effectively has the opening and closing points of a smaller cam combined with the area under the lift curve of a larger cam.
Engines with significant airflow or compression restrictions like aggressive profiles. This is due to the increased signal that gets more of the charge through the restriction and/or the decreased seat timing that results in earlier intake closing and more cylinder pressure.

Big cams with more duration and overlap allow octane-limited engines to run higher compression without detonating in the low- to mid-range. Conversely, running too big a cam with too low a compression ratio leads to sluggish response below 3,000 rpm. Follow the cam grinder’s recommendations on proper cam profile-to-compression ratio match-up.

Lift:
Another method of improving cam performance is to increase the amount of lobe lift. Designing a cam profile with more lift results in increased duration in the high-lift regions where cylinder heads flow the most air. Short duration cams with relatively high valve lift can provide excellent responsiveness, great torque, and good power. But high lift cams are less dependable. You need the right valvesprings to handle the increased lift, and the heads must be set up to accommodate the extra lift. There are a few examples where increased lift won’t improve performance due to decreased velocity through the port; these typically occur in the race engine world (0.650-1.00-inch valve lift). Some late model engines with restrictive throttle-body, intake, cylinder head runner, and exhaust flow simply can’t flow enough air to support higher lift.
Besides grinding a lobe with more lift, you can increase the lift of an existing cam profile by going to a higher rocker arm ratio. For example, small-block Chevys where the cylinder head runners are not maxed out may benefit from moving up from the stock 1.5:1 ratio to 1.6:1 rockers. But going up more than one tenth in rocker ratio can lead to trouble; there’s a limit to how fast you can move and accelerate the valve before the valvespring can no longer control the system. If a profile was a good design with 1.6:1 rockers, it’ll probably be unstable with 1.8:1 rockers. The correct solution is to design the profile from the ground up for use with high-ratio rocker arms.

Hope this is not too much information ("Information Overload"). I just want you to make the best choice with the information you know.

Good luck.

Prowbar

June 11th, 2023, 05:53 PM

Not a problem at all. I used cast iron guides for the exhaust, with the positive valve stem seals. Bronze would have been better, couldn't find any in the size I wanted. The engine is assembled, last thing is the cam, because I had some issues with it.

I've read a lot about cam design in general. Tried to stay very mild on the cam, to increase torque and drivability, and get as much out of the engine as possible. No need to try high hp/high rpm tricks if the engine doesn't turn past 3200 rpm.

Those Comp springs are pretty stiff I think but could work. I would prefer 85 pounds of seat pressure. Pete Chronis talked about Ford FE390 springs. For a low RPM engine, this should be sufficient in my opinion. A 5.9 Cummins uses about the seat pressure.

I'd like to increase lift but it has to be doable.

One way to increase lift is to reduce base circle size, there is indeed a possibility of running into geometry trouble.

I am going to discuss with the cam grinder if they can weld up the lobe to increase the lift and accommodate the new profile.

Different rocker arms are also possible. But would need to be custom-made.

Hope it makes sense.

lizziemeister'sV6

June 13th, 2023, 02:24 PM

Prowbar

June 13th, 2023, 03:25 PM

Was wondering what changes you are thinking about that differ from Pete's grind specs. I run a Pete spec ground cam - it sounds nice which was one of mine goals and seems to do good at highway cruzin' speed. My truck clocks at 60 mph about 2600 rpm. I think this is about where the power band comes in due to the cam grind. My truck sees mostly highway speeds and most generally pulls a car trailer lightly loaded. You can relate my truck's usage to that of 379 Peterbilt pulling a chrome reefer - gets the job done with a little flair. Sure there's better builds and combos but hey - it's a little different that any run-of-the truck - and it gets more looks that any 2023 decked out $100,000 truck when you pull up to gas pump.
I guess it's all in what you want - but the truth is anything you do to a 60 yr. old GMC V6 motor will never be equal to what a truck engine of today's manufactured engineered marvels can do in performance. BUT when we raise our hoods we CAN see a motor and are ABLE to work on it. This is just my thoughts - give me and other GMC V6 caretakers your inputs - for now I think I go out and crank-up the 1960's Diamond T "Cat" powered road tractor and blow some smoke while dreaming about a V12 powered "Crackerbox". Have a good day!

The reason for the changes is a comprimise between the stock cam and Pete's cam. A powerband of 2600 is a bit high for a 3200 rpm engine in my opinion. I like the low end torque and want to retain this. So a powerband around 1600-2000 or so. I hope to achieve this with the modified design.

Figured I added some info where I explain my reasons:
Most people agree that there are two key events in a camshaft: intake valve closing point and valve overlap. The others are important too, but not as much.
Generally speaking, intake valve closing determines the place where in the rpm range the torque is generated. Valve overlap has about the same effect. The intake can be timed later for higher rpm power. Valve overlap can be extended for higher rpm power.

Intake valve closing point:
The stock cam: 61-70 degrees ABDC, depending on the year.
Pete's cam: 46 degrees ABDC (After Bottom Dead Center)
Modifed design: 50 degrees ABDC - I agree with closing the valve earlier to up dynamic compression as much as possible.

Valve overlap:
Stock: 63 degrees, might vary with the year.
Pete: 33 degrees
Modified: 45 degrees - Searched the middle ground, as a compromise between the two.

I am thinking Pete's cam has a sweet spot at about 2600 rpm where the pulses act to charge the cylinders better. According to the 'books,' it should behave as a lower RPM cam.

Not trying to build a race monster, but hope to improve the usable power as much as possible.

Prowbar

June 13th, 2023, 04:35 PM

By the way, Lizziemeister, do you have any videos of your V6 running? Would love to hear what it sounds like.

lizziemeister'sV6

June 13th, 2023, 09:03 PM

I don't have one at this time - but I have see/heard my truck on video - I think someone on this site may have it. They commented that it sure didn't sound like a V-6. Next time 1 of my computer savvy buddies with a smart phone stops I will post a video.:thumbsup:

Prowbar

June 15th, 2023, 09:02 PM

Asked a local company that specializes in spray welding for repair work to build up the camshaft by spray welding. They advise against it due to the poor bonding to hardened surfaces, and the risk of the new surface flaking off.

Too much work and trouble for added lift. Might make custom 1.6 rockers in the future, we'll see.

I've sent the camshaft to the cam grinder today together with my specs.

Also took a look at the valve lifters - measured the face surface with a dial indicator by sweeping the lifter on a flat surface. The originals are cupped in (concave) from the wear. They should have a crown. (convex)

I also bought new Melling lifters to test, they have a flat face :banghead:

But, I also measured hardness with a Vickers tester of the lifter faces. I wanted to check the new Melling lifters vs the OEM lifters for hardness. I tested 2 of each lifter:
OEM lifters:
No. 1: 629 HV (56 hRC)
No. 2: 690 HV (58 hRC)

Melling lifters:
No. 1: 750 HV (60.5 hRC)
No. 2: 748 HV (60.5 hRC)

Interesting results. I figured the Melling lifters were much softer, low-quality pieces. Properly refaced, they should last a long time.

Now to reface the lifters. Since no one refaces lifters anymore in the Netherlands, I'm going to think up something myself...

Prowbar

June 15th, 2023, 09:06 PM

Here is the quickest way to pull the camshaft without removing the radiator support - just loosen the front engine mounts and use a jack to tilt the engine.

James

June 15th, 2023, 09:20 PM

Also took a look at the valve lifters - measured the face surface with a dial indicator by sweeping the lifter on a flat surface. The originals are cupped in (concave) from the wear. They should have a crown. (convex)

I also bought new Melling lifters to test, they have a flat face :banghead:

Now to reface the lifters. Since no one refaces lifters anymore in the Netherlands, I'm going to think up something myself...

The flat lifters should work as design. The camshaft lobes has a front to rear ramp on them to make the lifters spin.

Placing a crown on them would reduce the spinning effects.

On a side note, roller lifters camshafts does not have a ramp on the lobes. You do not want those lifters to rotate.

Prowbar

June 15th, 2023, 09:36 PM

The flat lifters should work as design. The camshaft lobes has a front to rear ramp on them to make the lifters spin.

Placing a crown on them would reduce the spinning effects.

On a side note, roller lifters camshafts does not have a ramp on the lobes. You do not want those lifters to rotate.

Yes, the camshaft lobes are ground on a slight taper, but the lifters should have a crown. Should they be flat, that would result in a line contact, which would wear rapidly. The crown helps break in and mating to the cam lobe. It does reduce spinning to an extent but helps distribute the load better due to increased surface area.

Take a look, this article explains it very well: To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic?

James

June 15th, 2023, 11:01 PM

Yes, the camshaft lobes are ground on a slight taper, but the lifters should have a crown. Should they be flat, that would result in a line contact, which would wear rapidly. The crown helps break in and mating to the cam lobe. It does reduce spinning to an extent but helps distribute the load better due to increased surface area.

Take a look, this article explains it very well: To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

Thanks. That was a good read. I always though the lifter was flat on the bottom. Having the slight crown explains a few things.

James

June 15th, 2023, 11:11 PM

This is what is needed for lifter regrinding.
 To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic?

tbucketnut

June 16th, 2023, 03:32 AM

Prowbar

June 16th, 2023, 10:46 AM

If you need lifters resurfaced, I deal with a well known cam grinder in my home town here called Delta Cams. I'm thinking it was $100 to resurface the 12 lifters. I have an extra set of these if you get into a pinch I send in to get resurfaced then sent to you.
Steve

Thanks Steve, I'll keep that in mind. I've watched some videos of Delta Cam on Youtube, Jon seems like a good guy. Have also read good things about the company.

tbucketnut

June 16th, 2023, 11:35 AM

They have been grinding my cams since back in the early 80's. When I was racing they built me a couple custom turbo cams for my 351 Windsor motor and I flew. Lots of experience there and they gotten a lot of people needs straightened out.

Prowbar

June 21st, 2023, 09:38 PM

The camshaft has been sent out last week for regrinding. Hope it doesn't take too long.
In the meanwhile, there are smaller jobs that needed to be done:
-Leaking rear axle wheel seal (replaced both sides, those were one old seal and one seal with an adapter ring I made. The adapter ring started to leak unfortunately, so I took it out and replaced it with the correct seal)
Cleaned out the axle hubs and bearings as well. Bearings are from Timken, made in the USA. They look absolutely spotless. Replaced the rear-end fluid a few weeks ago.
-Clean up the alternator to make it match the new engine. Sandblasted and repainted the fan and used steel wool to clean the aluminum housing.
-Repainted the voltage regulator cover.
-Repainted the pulleys and fan. Wasn't happy with the first try.
-Repainted the valley cover, also do touch-ups on the intake manifolds and heads.

Now it is the time to tackle these tasks. Man, I miss driving the old beast. Should be fun with the new engine.

Prowbar

July 11th, 2023, 06:12 PM

Completed all the tasks from the last post. Now onto cleaning up some of the wiring, and installing items such as the AFR meter. Hope to complete the exhaust downpipes this week as well.
Then onto some small jobs, that still needed to be done.

Communication with the camshaft grinder hasn't been too great, still waiting. Companies here are not great to deal with. Wish we had a company like Delta Cam here.
The issue here was that they take apart their camshaft grinder for cleaning every 10 years or so. Guess who wanted to grind their cam while they had the thing apart? So they told me it would take a month to put it back together. That was on the 24th of May. 24th of June has since passed, and more than 2 weeks have passed since then.

In the meanwhile, Steve (tbucketnut) has helped me a great deal by sending out his spare sent of lifters to be reground by Delta Cam for me. Much obliged Steve, and I'm looking forward to them.

If this camshaft grinder doesn't work out, I'll be sending the camshaft to Delta Cams as well... Hopefully, it does not have to come this far.

Prowbar

July 14th, 2023, 03:14 PM

Steve told me that he brought some 305 V6 camshaft cores to Delta Cam. I called them and asked if they could grind one of those for me. About a week turnaround time they told me. Hope this all works out. They do ship worldwide.
I also gave them my custom grind specs to grind on the camshaft.

I canceled the order from the other company.

Man, I can't wait for the camshaft to arrive here.
Running out of small jobs to do in the meantime.

Prowbar

July 14th, 2023, 10:02 PM

Here is the exhaust downpipe work. I reused the old exhaust flanges that I faced on the lathe. I reworked existing gaskets to fit this application. A pipe reducer from the stock 2.5" to 2.25" was then welded on. The rest of the exhaust is 2.25", which should be plenty of exhaust for this application.
In the picture, the left side is fully welded but the right side is only tacked together. This is now fully welded as well. Quite a route getting around this oil filter. Exhaust work is fun to do, once you get the hang of it. It is a shame that when you finally get the hang of it, the exhaust is as good as finished.

I used a pipe reducer to create the slip fit for the rest of the pipes. A clamp is used to create a gas-tight seal.

My welding skills are not quite good enough to lay a continuous bead on a thin-walled exhaust pipe without creating holes... So this is a fish-eye paradise for the welders.

In the second picture, you can see the position of the O2-sensor. The nuts are still to be welded on, someone will TIG-weld these for me. Both pipes have a nut for the O2-sensor but only can be used at a time. A threaded plug is supplied and screws into the nut in place of the O2-sensor.

tbucketnut

July 18th, 2023, 04:16 PM

Coming along nicely. I take it you have a planned electronic FI system planned correct?

Prowbar

July 18th, 2023, 04:39 PM

Coming along nicely. I take it you have a planned electronic FI system planned correct?

Thanks, Steve. The O2 sensor serves as a display instrument only for now. The engine will run most of its life on propane, and this is fed via a mixer to the carburetor. The system is from Impco. It is a dual fuel system, implying that gasoline can still be used.

Here is a video I made showing off my propane system: To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

Liquid propane injection with injectors is possible but would require a custom manifold. I like the simplicity of this setup.

Prowbar

July 21st, 2023, 07:31 PM

Another update. Delta Cam should have the camshaft finished today, or Monday next week. Hope to receive it the week after. Lifters are also still on the way.

Been busy working on the GMC. The exhaust is pretty much finished. The O2 bungs were welded on for me - beautiful work. If this exhaust ever rots out, I'll let her TIG weld the whole exhaust for me :upyes:
The O2 sensor and the gauge are installed and it all works.

Been busy with the carburetor - managed to score a 500 cfm Holley locally for cheap. Basically a brand new carburetor. It has 61 jets now, which are probably too small. I did some looking around on the forum, most seem to use 68s for the 305. Pete said that the stock 73s worked well with the 478, so that's what I'm using as a baseline. Should it run too rich or lean, I can adjust jet sizes according to the O2 sensor readout.

On Amazon, they said that they shipped the jets to the Netherlands, turns out they do not. So have to ask some local guys if they have Holley jets.

It also has a no. 8 power valve, ie. it opens at 8" Hg. From what I've read the power valve should open at half of your idle vacuum, so 8 seems about right. It also has the stock 30cc accelerator pump.

This does mean that I'm plugging off the governor line, which I first intended to keep in place. I am playing around with the idea to hook a normally open oil pressure sender to the governor line, and if it senses oil pressure a buzzer would sound indicating you hit the redline. Though a nice tach would be better. Would love to have a nice vintage tach on the steering column. Any tachometer recommendations, let me know.

Made a nice adapter flange to use the 478 manifold, but am running into hood clearance problems with the propane mixer. Decided to go back to the 305 manifold, and use the available Mr. Gasket adapter. I'll be sure to radius the edges in the manifold to allow for more flow to the middle intake runners. The port size is the same on the 305 vs the older 478 manifolds. The difference is the carburetor bolt pattern and the 478 manifold has a built-in spacer - see picture.

Since the Holley uses the standard 5 1/8 air cleaner base, readily made propane mixer adapters are available, so I bought one and modified it somewhat to reduce the height. I corrected the center bolt hole and also made a bushing to better accept the 1/4 thread diameter and nut on the Holley. See picture.

I am resizing the pictures for the forum from now on, so they should enlarge quickly now. Took a while to load before!

Ed Snyder

July 22nd, 2023, 12:58 AM

Would love to have a nice vintage tach on the steering column. Any tachometer recommendations, let me know.

Both ISSPRO and Datcon make 3-3/8" diameter 0-4000 tachs that match our speedometers pretty well. First photo is the ISSPRO in my '62 Suburban. Second photo is the Datcon in the '66 pickup that Clyde in South Carolina owns now.

See To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? and To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic?

Prowbar

July 25th, 2023, 07:31 PM

Since I'm using the 305 V6 intake manifold, I blocked the heat riser in the intake manifold using the same method as before, which is to mill out a recess for a plate to fit in. They are a light press fit. These block the exhaust gas from the heads from entering the intake to preheat the manifold. This is a modification for propane usage. Though it would work for gasoline as well, but in hotter climates. Cooler air means a denser charge, ie. more power!

The correct Mr. Gasket carburetor adapter is on order, as well as the missing gun rack that was once installed in the truck.

I also removed the governor line.
Scored a nice vintage Sun tachometer on eBay, which was local to me. 15 bucks with 15 bucks shipping. It is a 3000 rpm tach, wish it would have been 4000. Though I should keep it below 3000, the 478 was governed at 3200 rpm.
Old Sun tachometers need a separate transmitter box to work properly. However, I know someone that is pretty handy with electronics, and we're going to see if we can rework one to work directly with the HEI tach signal.

Still waiting on the camshaft and lifters. Still working on all sorts of small jobs that need to be completed.

Ed Snyder

July 26th, 2023, 05:29 AM

Scored a nice vintage Sun tachometer on eBay, which was local to me. 15 bucks with 15 bucks shipping. It is a 3000 rpm tach, wish it would have been 4000. Though I should keep it below 3000, the 478 was governed at 3200 rpm.
Old Sun tachometers need a separate transmitter box to work properly. However, I know someone that is pretty handy with electronics, and we're going to see if we can rework one to work directly with the HEI tach signal.

Here's a photo of the Sun tach in my '65 Suburban that Dad bought new. He had the dealer install the tach and clock before he took delivery.

Prowbar

July 26th, 2023, 09:32 PM

Thanks for the pictures, Ed. That is not the typical Sun tach I've seen in other 60-66 trucks. You're making me want to cut a hole in my dash :ahhhh:

First I'll have to get the thing converted.

Prowbar

July 31st, 2023, 08:54 PM

Good news! Delta Cam (finally) finished the camshaft!

This is the custom grind that I wrote about earlier. Reground lifters are also on the way!

Hope to have camshaft here in about 1.5-2 weeks.

Fingers crossed...

I'll tell ya, when I have that bumpstick in my hands, that thing is going into the engine ASAP :upyes:

Prowbar

August 10th, 2023, 08:59 PM

Received the reground lifters yesterday. They are very nicely ground and then polished with ceramic media, resulting in a very nice finish. The correct radius has also been ground in, if you put two lifters with the faces against each other you can rock them back and forth. Thank you very much, Steve.

Also installed the missing gun rack. The holes were there, and I like the touch as a firearms enthusiast. Just something an old pickup should have. Can't drive around with guns in the rack though :teehee:
Need to remove that duct tape in the cab, but it is stubborn stuff... Been on there for years.

Also did some mocking up to check all the carburetor linkages. Made a steel fuel line as well. The fuel filter is placed between the frame rail line and this steel line. This prevents the gas in the filter from boiling and flooding the carburetor. I had problems with this in the past.

Prowbar

August 10th, 2023, 09:15 PM

Here are the modifications to the 305 manifold. I received the Mr. Gasket adapter. To clean up the gasket surfaces I fly cut them on the mill.

I then opened up the manifold to match the adapter opening. I also radiused the edges of the manifold where it transitions into the runners. It is easy to rough in with the carbide burr, then followed up by a shoeshine motion with a thin strip of sandpaper to dress the edges.

Both modifications should aid in flow tremendously.

As you can see I also installed the block-off plates for the heat riser. They are a light press fit.

Also got new 73 jets for the Holley from a local guy, he had a set of Holley jets. Said I could come back if I need another size.

I have plenty of hood clearance now, but I don't like the look of the stock Impco mixer filter. Toying with the idea to adapt a 1-inch or more dropped base air cleaner adapter on the mixer and use a 14x4 or 5-inch filter to correct the proportions.

The camshaft is on the way, hope to avoid any unnecessary customs intervention so I can install it ASAP.

James

August 10th, 2023, 10:08 PM

I then opened up the manifold to match the adapter opening. I also radiused the edges of the manifold where it transitions into the runners. It is easy to rough in with the carbide burr, then followed up by a shoeshine motion with a thin strip of sandpaper to dress the edges.

Both modifications should aid in flow tremendously.

I had done the same modification to my intake manifold that you had done for the carburetor flange. However I did flow testing with a head on a flow bench, intake manifold bolted to it, and a Holley carburetor on top of that. The result that I had found is the center cylinders did not flow as much as the end cylinders. However with the stock carburetor all of the cylinder flow about the same (and flow alot less than the Holley). The center intake runner make a sharp turn toward the cylinder. To resolved this, I removed the runner divider between 3-5 and 4-6. Now with the Holley all of the cylinders flow rate are close together.

The other reason I'm improving the flow was I modified the combustion chamber and intake port to improve the air flow and cylinder swirl. Before there was no swirl. Now with all of the modification I had improved the overall flow rate by 10 cfm at .450" lift and the swirl inside the cylinder is 900 rpm at .450" lift.

Prowbar

August 11th, 2023, 03:40 PM

Now that you mention that about the runners, James, it reminds me of an old post where you posted some pictures: To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? Post 6.

Looking to do the same thing to my manifold, since you've proven it works.

Curious how you removed the divider. Just roughed it out with a carbide burr from both sides?

Also curious about your head porting work. I figured the stock ports should produce some swirl, but apparently, they do not. 10 cfm is a nice gain though. Was that with a 3-angle valve job?

James

August 12th, 2023, 02:09 PM

Looking to do the same thing to my manifold, since you've proven it works.

Curious how you removed the divider. Just roughed it out with a carbide burr from both sides?

Also curious about your head porting work. I figured the stock ports should produce some swirl, but apparently, they do not. 10 cfm is a nice gain though. Was that with a 3-angle valve job?

I used a 6" length carbide burrs and worked it from both ends. I have this intake on my truck now. Road testing it I can pull a steep hill and still have power to accelerate up it. Before I would slow down. I'm planning on placing my truck on a chassic dyno to compare to the stock pull (stock carb, intake manifold, and breather).

First off I have not had the time to see what the results will be from this point on, life happens. All of the work that I have done so far was over a year ago. And I been wanting to get back to finishing it.

In the intake port valve pocket I reshaped the short radius, and some smoothing of the port. After a 3-angle valve job I made sure the transistion from the port to the bottom angle was smooth.

As far as the swirl, I had bolted my flow bench adapter onto the head and scribed the bore onto the head opposite side from the sparkplug. It basically convert the sharp edge (that shroud the intake valve) from the edge of the cylinder to the top of the combustion chamber into a ramp. Making a smooth transistion. The only major problem with this is it lower the compression ratio. There is two processes I will be performing to help bring the compression back up:

1.Cutting the head deck and the block deck. I believed the decks is thick enough not to cause an head gasket sealing problems. Will also need to make sure the block head bolt holes is fully tapped and clean to allow the bolts to go in without bottoming out.

2. Then I am going to offset grind the crankshaft from standard to .030" under to increase the stroke. Then mill the top of the piston to get the deck height back to zero, this will remove most of the dish from the top of the piston.

Both processes should raise the compression to approx. 9:1, hopefully or close to stock.

On another note: Doing the same thing on the exhaust valve (but on both side of the valve) will improve the exhaust flow by 15 cfm, with an open exhaust port. Not able to test this with the exhaust manifold bolted on because the flow bench is in the way.

Prowbar

August 12th, 2023, 03:54 PM

Thanks for the reply, James. Time to rework the intake... Seems you gained some hp and torque performing those modifications.

Hope you get around to performing the dyno testing, would be interesting to see. A dual exhaust would also help in your case I would think.

I did the same as you to the 478 heads. The short side was a sharp ledge going transitioning into the valve seat area. I radiused it. Also added the 3 angles.

I like your idea, but how much do you need to take off of the deck to get rid of the dome in the piston? The offset grind sounds good but a lot of work. Then you run into the intake manifold and water cross-over fitment problems...

James

August 12th, 2023, 05:15 PM

I like your idea, but how much do you need to take off of the deck to get rid of the dome in the piston? The offset grind sounds good but a lot of work. Then you run into the intake manifold and water cross-over fitment problems...

I hoping to get about .020"-.025" longer stroke, so the piston will move up .010"-.012" higher in the bore. I facts you might not need to mill the piston if the head gasket thick enough (.055" stock thickness) and it would raise the compression ratio, currently the stock piston deck height is 0.00". I've seen other engine with a piston deck height above 0" because of the gasket providing clearance. They did this because they needed more space for the top land and using a short piston pin height.

The intake flange on the head will need to be milled to allow the intake manifold to sit properly. This way the heads and intake manifold can be swapped with another block.

Prowbar

August 21st, 2023, 03:59 PM

Got the camshaft in Saturday! Delta did a good job, but the results ticked me off a little at first as they measured them as a hydraulic camshaft. Therefore the opening and closing points have to be taken at the 0.012" and 0.018" lash settings. Seems they had a core with a little flattened intake lobe, as the intake lift isn't as high as I hoped it to be. I believe the stock rockers are 1.5 as opposed to 1.73 which is written down. We'll see how it runs.

Anyway, this probably being an earlier cam(?) it has very small oiling grooves for the heads. I milled them out and also increased the oiling duration to the heads. I am a firm believer that this is better for the engine and positive valve seals. I will try to bleed the trapped air from the rocker shafts when priming the engine by loosening one of the end bolts.

The camshaft and reground lifters have been installed since.

I am also modifying the intake manifold as per James' instructions to remove the 1-3 and 4-6 dividers. It is a hassle to do, but should provide equal flow to all runners. Should have gotten a Magnum manifold, since it already has the dividers removed. But it would have to be imported and freight will cost me an arm and a leg. Anyway, hope to fire her up this week.

Prowbar

August 23rd, 2023, 04:24 PM

Over the last few days, I reassembled the engine and front end. Started her up and broke in the cam.

Modified the intake manifold as per James' instructions, thanks for the tips James.

Took her out for a test drive. This thing pulls like a freight train... Literally twice the power of the 305. And amazing throttle response. Had her up to 3200 before I blinked. Need a rev limiter badly, going to buy an MSD 8727CT when the vendor here gets it back in stock. This is a HEI rev limiter that can be set between 3000 and 9900, so ideal for this application.

Also found out that these Walker 18230 mufflers choked up the engine pretty badly. They neck down internally. Immediately ordered Walker 17613 mufflers. These have internal baffles but do not neck down. Advertised as Mega Flow. Should be quiet when cruising but loud when you step on it.

Also found out that the SM420 trans can use new bearings... Never noticed it on the 305 because of the lower power output.

The stock clutch seems to hold up though, which kind of surprised me.

Haven't even tested it on gasoline yet, it should have even more power compared to propane.

So to anyone considering rebuilding a 305... Ditch the thing and get a bigger V6... You won't regret it.

Videos to follow.

tbucketnut

August 24th, 2023, 12:29 PM

David, can you send a short vid through say through Whats App? I would love to see and hear your engine perform. It sounds really stout. Glad you are happy with the results. Funny how the power restrictors quickly show up like you mufflers. Too bad you are not in the Pacifi Northwest, I have a work area just for rebuilding the sm420's and a rebuild kit ready to go.
Congrats,
Steve

Prowbar

August 24th, 2023, 10:46 PM

Hi Steve,

Sure, PM me your phone number (with the country code, ie. the full number) and I'll send you (or anyone else) some videos of the 478 running. Still need to upload them to YouTube.

The SM420 bearing noise was slightly present at first but seems to have vanished now. Maybe because the new gear oil finally has found all the crevices in the transmission. Works like it should now even shifts great into 2nd gear.

I'm going to do a driving video as well, these will follow soon also.

The mufflers make the engine sound like it has a cold, really odd. Didn't have that with the 305. Hope to receive the new mufflers tomorrow so they can be installed.

Tried gasoline today, and got the idle right, about 14:1 AFR. The 73 main jets are too large it seems. The AFR gauge went to 10 when transitioning into the main circuit :ahhhh: and the engine stalled when I let off the throttle. I've set the float level correctly. Probably going to 68's and start there. The power valve opens at 8" HG and the idle vacuum is 15" HG, so right on the money there.

Driving is fun but requires a careful right foot. In 4th gear I can pull from 20 mph to 50 mph in one go, it just pours out the torque like it's nothing. And it'll get a 5000-pound truck moving for sure.

James

August 25th, 2023, 01:48 AM

Tried gasoline today, and got the idle right, about 14:1 AFR. The 73 main jets are too large it seems. The AFR gauge went to 10 when transitioning into the main circuit :ahhhh: and the engine stalled when I let off the throttle. I've set the float level correctly. Probably going to 68's and start there. The power valve opens at 8" HG and the idle vacuum is 15" HG, so right on the money there.

After all of the intake work on my 305, my main jet is a 71. My truck has a lot more power.

Prowbar

August 25th, 2023, 11:48 AM

After all of the intake work on my 305, my main jet is a 71. My truck has a lot more power.

Interesting. Have to do more testing and experimenting to see what causes the running rich situation.

Prowbar

August 26th, 2023, 06:36 PM

Quick video of the engine running: To view some links or images in this forum your post count must be 1 or greater. You currently have 0 posts. Maybe you should introduce yourself with a new topic? 

Driving video to follow. Haven't messed with the carb jetting yet, it is running really good on propane.

Prowbar

September 27th, 2023, 09:15 PM

Been a month, not without its fair share of GMC action...

The bearing noise in the old SM420 started to get worse, figured it was time to do a transmission rebuild. Ordered a rebuild kit and new synchro's that arrived very quickly. Removed the trans and started the rebuild process. Used the solvent tank to clean all the parts, you'd be surprised how much old oil and sludge are present in every nook and cranny.

Disassembled everything, cleaned all parts, and assembled them with regular engine assembly lube, which easily dissolved in the gear oil.

Quite a fun transmission to rebuild. The rear ball bearing of the secondary shaft was pretty stubborn to get off, so I removed the outer ring and cage and welded up the inner race. Using a bearing puller it finally sprung loose.

All the gears looked excellent, but the bearings had a lot of play but did not look as bad as I thought they did. They were still the original New Departure bearings.

Ultimately there is no need to get all the fancy tools as described in the manual, if you use your imagination you can rebuild the trans with a shop press, some snapring pliers, and a set of bearing pullers.

The new transmission sounds and shifts great. Very satisfied with the results.

As for the HEI ignition, I had 2 modules fail in a short time. First the original developed a misfire the night before. The next day it would not start. Replaced with an OEM GM module, it lasted about 2 weeks, then quit on the same note. Now on the 3rd module. Installed it today and it runs well, hope it lasts a while this time. Checked all the wiring for shorts of problems, but couldn't find any. Getting a proper 12V signal to the BAT. Tach port is fine too. The coil and magnetic pickup all check out fine regarding resistance. The only thing that I can think of is the distributor ground, which, using the original hold down, could see why it would cause trouble. I modified the hold-down with some brass pins to improve the ground signal and hold-down ability with the HEI as the base is smaller in diameter than the points distributor.

Nothing else to report other than I am tweaking the jet sizes for gasoline. 73s were much too big, I dropped them to 66s and ran about 13.2 AFR in the main circuit at cruise. Still too rich for me. Probably change them to the original 61s to try and achieve get a 14.7-15 at cruise for fuel economy.

Also installed the new Walker 17613 turbo-style mufflers. These don't have the necked-down internal piping as the old mufflers did. They sound great but are a little loud, though. Might have to quiet them down some.

Seems the engine is fully broken in now, the plugs look great and the valve lash is stable.

Prowbar

September 27th, 2023, 09:17 PM

Here are some additional pictures of the transmission install as well as the modified distributor hold-down. The transmission install "bridge" was something I borrowed some someone who made it for his truck, which also has the SM420.

FetchMeAPepsi

September 28th, 2023, 12:53 PM