Got a 478...
 

Always wanted to get a bigger V6 than the 305 that I now have... Yes sir I found one. To find one of these in the Netherlands, especially a 478, is a one-in-a-million chance...

A standard, non magnum 478. Complete engine with new gasket set, although in parts at the moment. With all the large truck accessories, such as bell housing, flywheel, clutch, air compressor, generator, brackets, etc. If you're looking for large truck accessories I'd be happy to help.

The engine is in very good condition and looks to be a fairly low mileage engine. One of the exhaust valves is burned though, will need a new one for that, or have this one repaired.

My plan is to build this engine to replace the 305 that is now in my 1500.
It will be a stock rebuild, with a couple of minor modifications.

I've been studying Bigblock V6's posts on his 478 swap, but still have a couple of questions. If we could come into contact that'd be great!

The plan is to convert the engine to use all the light truck accessories, such as the bell housing, water pump, and timing chain.
Will have to fab up a flywheel and have it balanced.

My guess is that the engine is a 62, one of the first 478's. No PCV valves in the head, but does have the fresh air canister on the back left side. My guess for a 62 is the fact that it came with a generator instead of the alternator.

Your thoughts?

Re: Got a 478...
 

i just sent a message to bigblockv6 over on his facebook profile for you. good luck with the '62 478!!!!!!

Re: Got a 478...
 

Thank you very much Lewis! Checked out BB V6's profile, seems like he hasn't been active on the forum for a while.

Re: Got a 478...
 

Correction: there are PCV valves in the heads, and I just found a replacement exhaust valve in one of the boxes! Couldn't be happier. Here are some pictures:

Re: Got a 478...
 

You will sure like the 478. I drove one for years in a '62 6500.

Sure is a powerhouse.

Re: Got a 478...
 

just got a message from you from BB V6. he said his e-mail is down, but you can catch him on Facebook Messenger. you will find him under Peter Chronis.

Re: Got a 478...
 

Will do. Thanks.

Re: Got a 478...
 

Is Pete banned or something? Haven't seen him around in a while.

Re: Got a 478...
 

Been chatting with Pete on messenger, will ask him what's going on.

Re: Got a 478...
 

Cleaned up the major grime off the heads. Removed the valves, no surprises. The valve springs are pretty stiff though. The guide from the burned exhaust valve needs to be sleeved, as it has more play than the others.

I will also have the heads professionally cleaned, decked and have hardened seats installed in the intakes.

The castings, as from the factory, are pretty bad regarding port design. The exhaust passages faily are restrictive compared to the intakes. But the worst thing is the short turn into the into the head has a very sharp ledge above the valve seat. I am working to radius these to create better airflow. Both intake and exhaust have these sharp ledges. Also the exhaust ports really need to be cleaned up, they have ledges in them. I removed these also.

I also lightly broke the sharp edges in the machined combustion chambers.

That's as far as I'm gonna go with the heads.

Re: Got a 478...
 

Just talked to him and he can't log on because his phone broke down and locked his info. He wants to get back on but hasn't taken the time to do so.

Re: Got a 478...
 

Took the time to get everything measured on the 478. The wear is a little more than I first anticipated, but most falls on the outer end of the spec. A loose engine is a happy engine...

Also discussed basically everything with BB V6 about these engines, thank you very much for that Pete.

There's wear in the cylinder bores but I'll just re-hone them and re-use the existing rings. The pistons look good.

As you can see I disassembled, then decked the heads and exhaust ports.
The heads and block are now at the machine shop for sleeving of a couple of worn valve guides, and having the block cleaned. Positive valve seats will be installed also.

I first wanted hardened seats on the intakes (exhausts have them from the factory), but there is little meat in the intake runners for a seat. While it will be run on propane, it will not have to work hard in my pickup, and combined with these engines' excellent cooling capacity it should not be needed really.

The block will only be washed at the machine shop. Got most of the parts in for the rebuild except for the rod bearings. Main bearings are still in spec, and good to use.

The exhaust manifolds are badly warped and the (previous) mechanics tightened the bolts way too much to try to get it to seal again. Almost every bolt 'ear' has a crack and will need to be brazed back together, milled, then painted in factory yellow.

Re: Got a 478...
 

Got the clean block from the machine shop. The heads are still there.
Got all the parts in: rod bearings, core (freeze) and oil galley plugs, timing chain, etc. Also bought me a Buick V6 even fire HEI to convert and use. This should definitely help with a cleaner burn in these massive bores.

Build me a homemade heavy-duty engine stand from an old engine hoist which was scrap iron. Works really well.

Now all that left is a re-hone of the block and then I can start on the short block assembly. Can't wait to get this powerhouse in my truck!

Re: Got a 478...
 

Finally got around to hone the block. Also included is a picture of my homemade engine stand.

First I had to mill some spacers to use our hone for these massive bores. Then we honed the existing bores. There's more wear than I like, and not all of it has been honed out. However, I'm confident that this will produce sufficient results.

After all, this is kind of a budget build, and while an overbore might be better, where are you going to get oversize pistons from anyway?

First honing job has been done with coarse stones, to get a good crosshatch in the cylinders.

Because this engine will run on propane from the start, the rings will not really seat in the bores because of the superiority of propane fuels when it comes to preventing cylinder wear. Now I read about this trick a while back in an IMPCO book, which article I posted here on the forum which was about 401 V6's converted to propane.

In that article, they had troubles with the rings seating with the freshly rebuilt engines running on propane from the start. This resulted in excessive oil consumption. They solved this by seating in the rings with a mixture of Bon Ami and a thin oil and turning the engine over by hand. I will be doing the same thing, which involves assembling the engine with crankshaft and pistons, followed by seating the rings by turning over the engine, then taking it apart to clean the parts thoroughly. I'll see whether the first ring will seat with this method as it is still the original chrome-plated ring. Then I can assemble the short block for the last time.

In doing this, I should also achieve a plateau honing effect, which means that the peaks of the material left by the coarse hone will be evened out. The valleys created by the coarse hone should then be still present for oil retention purposes.

I added the article down below. When enlarged the orientation is good.

Re: Got a 478...
 

Update: touched up the crosshatch in the cylinders to get complete coverage in the cylinder walls.

Coated the cylinder walls with a mix of ATF and Commandant red (which is a coarser polishing compound)

Assembled the crank, rods, and pistons in the block with assembly lube. Noted the position of the piston rings.

Turned the engine over by hand for about 100 turns, re-applying the coating in between. After a while, you can see a good, even thickness of the mixture on the cylinder walls with small vertical lines. Difficult to see in the photo. When I was satisfied I disassembled the engine again and cleaned the block with a lint-free rag and ATF to get the grit out.

Cleaned the pistons in the parts washer. Re-lubed everything, and installed the rear main seal. Then installed permanently.

After breaking in the crosshatch, it looks like a plateau-honed finish. Very satisfied with the results.

About the pistons: nowhere in the book is there mention of piston orientation in the block. nor can I find anything on the internet. No marks or arrows either on the pistons. Are they unidirectional?

Still need to install the plugs that came in the rear main seal kit into the 1/2" bolts in the rear main cap.

For anyone thinking that engine stand is about to collapse because the block hangs crooked, it isn't. I used standard diameter pipes for the inner and outer mount point on the engine stand and they have a lot of room between :)

Re: Got a 478...
 

More pictures.

Re: Got a 478...
 

All of the GMC V6 pistons has a ZERO piston pin offset, so they can be installed in either direction. I did find a single reference on the Internet that made reference to the piston offset and it had stated it was 0".

I thought I had saved that info but I can't find it now.

Re: Got a 478...
 

James, excellent, thanks.

Re: Got a 478...
 

Ok, it's been a while... But I've been hard at work on the 478 parts.

I managed to get my hands on a spin-on oil filter adapter, which is sweet.

The exhaust manifolds are almost completed. They were a mess, every ear on one manifold was cracked, one broken off. Probably because of exhaust leaks and the mechanic over-tightening them. Now I ground out the cracks and brazed them with brass rods. I also brazed on a new piece for the missing ear. I then removed the excess brass. After that I've milled them flat. There are two 'studs' in the casting, I believe those are factory locating pins for the millwork. A bolt with a shallow hole in it locates on that stud and the nut is used for adjustment. It took some work getting them flat.

The heads are also back from the machine shop, however, I have a small change of plans. Pete Chronis told me to get rid of the sodium-filled exhaust valves. They were known to snap and I don't want to take the risk. He also said some CAT valves would work. No CAT valve will work, however, I found a Cummins exhaust valve (3902254) that is basically identical to a non-magnum 478 exhaust valve, same head dia, stem length, non sodium filled. Therefore the stem is smaller at around .375" compared to the original 7/16" exhaust valve stem. Now the exhaust valve guides could use sleeving anyway. Therefore I am going to make bronze guides that will incorporate a positive valve stem seal. The valve stem seals are already installed on the intakes.

Also the big elephant in the room: the flywheel. I first figured turning a flywheel from a piece of plate myself. I have a donor 305 flywheel for dimensions. Now I went ahead and did some measuring, which I should have done first :) My 478 came with a round SAE truck bellhousing. Its flywheel is the same diameter as the 305!! However, it uses a larger clutch, pressure plate, pilot bearing and a coarser starter gear.

Now I am converting this flywheel to the 305 dimensions. As you can see I first removed the ring for the larger pressure plate. I then milled the step and drilled and tapped the holes in the clutch face for the pressure plate. Next up is to make a sleeve that presses into the pilot bearing bore to convert to the smaller pilot bearing. Still need to final grind the flywheel and turn the sleeve, and switch the starter gear.

Very satisfied so far with the progress. Lots of machine work but well worth it.

Re: Got a 478...
 

OEM valve left and Cummins valve on the right. I'm probably going to add a small back cut to remove that awful ridge after the seat cut.

Re: Got a 478...
 

Finished the flywheel today, ground the flywheel flat for the last time, made the conversion sleeve for the pilot bearing and pressed it in, and installed the starter gear from the spare 305 flywheel. There are some surface cracks but nothing cracked through, I'll be running it this way we'll see how it goes. Thinking it'll have plenty of life left.

Now onto the cylinder heads. Going to have to modify and install exhaust valve guides. I found valve guides from a Volvo Penta engine that will be usable for my conversion. These guides will be modified to accept good valve stem seals.

A 3 angle valve job is also on the list.

I'm also looking into a modification on the idler gear that will allow me to run the gear setup with the 305 timing cover, this will involve some machine work also. Some say it cannot be done but I'm not a believer yet... :ahhhh:

Re: Got a 478...
 

Happy little manifolds...

In factory yellow. It grows on you :)

Pete Chronis told me that the manifolds were painted with yellow exhaust manifold paint. When assembled on the engine, the complete engine was then painted red, including the manifolds. As the red paint could not withstand the heat, it burned off and revealed the yellow paint underneath.

I found a trace of both red and yellow paint on the manifolds. On my 305 there is quite a lot of yellow paint left, including on the Y-pipe.

Next up: head work. I have to drill out the original guides, modify the new guides and press them in the heads. Then valve-related work. Still, lots to do but coming along slowly. Have lots of new parts to go on there including motor mounts. I cannot wait to pull out the 305 for the 478. Should make a ton of power.

When the 305 is out I am going to complete the frame paint in the engine bay, and paint the firewall in 503 light green.

Re: Got a 478...
 

It's been a while. Coming along slowly as usual...

First off I finished the intake manifold. I bead-blasted the old paint off and machined the gasket surfaces. Usually, I don't bead blast anything, but the paint was in pretty bad shape and the whole intake was full of rock-hard carbon deposits. When disassembling the heads I also noticed a lot of carbon buildup, it probably used a lot of oil when it was still running. Bead blasting was the only way to clean the insides of the intake. I also cleaned up some of the rough casting spots in the runners.

FYI: The intake manifold angle between the gasket surfaces is 88 degrees. Very odd angle, luckily we have a large milling machine that has a head that can be angled in order to fly cut the surfaces. We also have a small mill that can tilt both the head and bed (in 2 ways). Very versatile machine to have.

As I say in every post that this engine will run 99% of the time on propane :teehee: I'm implementing some tricks to get better performance on propane from the engine.

On my old 305 with its rusted heat riser (which I wired open later) the intake always got hot. With propane use, this is not satisfactory. Therefore I machined pockets in the intake exhaust gas passages in which a block-off plate will be mounted. This blocks off the stream of exhaust gas from entering the intake manifold, keeping it cooler. It is easy to remove the intake to remove the block-off plates or drill a hole in them to fine-tune the intake temperature if wanted.

Still working on the heads. I machined valve guides and reamed out the exhaust valve guides. More pictures and info on that later, however, I installed the valve guides in the first head today. They are a very light press fit and they have a shoulder so they can never fall into the combustion chamber. A positive valve stem seal can be mounted on top of the guide, which will be installed later. Now onto recutting the seats, with a 3-angle valve job.

Also modified the exhaust valve retainers to accept the Cummins valves and keepers. They are a little larger and have a slightly narrower angle. I made a simple fixture to recut them in the lathe. A little finetuning on the angle and it was spot on.

More to come, when the head work is finished I can start assembling the engine. Still have a couple of things to do such as modifying the idler gear to work with the 305 timing cover, finishing the oil filter bypass valve, and adding a ported vacuum source to the carburetor, and exhaust flanges.

I'm making a bypass valve for the oil filter because the original piece got lost in the mail. I'm making one after my own design, which should be an improvement in regards to the plunger bouching and chattering on its seat. More on that later.

Re: Got a 478...
 

Here is the modification for the idler gear. To use the 305 timing cover with the gear setup you have to shorten the length of the idler gear nose or snout as it sticks out too far. The 478 timing cover has a large dimple cast into it to house the snout. This idler gear is pretty over-dimensioned. it gets fed with a continuous supply of oil from the main oil galley. I figured a little less bearing surface wouldn't hurt a thing. The idler gear assembly was still as tight as the day it left the factory.

After measuring the depth of the 478 cover I chose to shorten the snout to fit the 305 cover. The depth of the cover is about 36mm (1.42"). The stock idler gear is about 56.5mm (2.23") including the bolts to retain the front plate.

I went ahead and indicated the idler gear shaft, which was then shortened by about 9/16". I also polished the surface. I tapped the old oil supply hole and screwed in a set screw is retained with LocTite. A new oil hole is drilled opposite the old hole to supply the oil. I then made a tool to press the bronze bushing into the idler gear 9/32" (half the distance) deep. This lined up the oil groove in the bushing with the new oil hole. The existing 5/16 UNC holes were tapped deeper and a new front plate was made, with uses countersunk fasteners to reduce the depth. It is coated on the inside with LocTite gasket sealer to cap off the oil galley. These bolts are also secured with Loctite. I tried to reuse the oil front plate but it was too hard to machine.

The idler gear was then indicated and shortened in the lathe by the same amount, keeping the stock axial play in the setup. The total length of the assembly from the engine to the front plate is now a little less than 1.42". There's always a little variation in the casting which means I have to grind a little clearance into the timing cover, but that is no issue since it is very little material. I did not want to shorter the idler gear any further because I would intersect the old oil galley that I now capped off with a set screw.

Machining was surprisingly easy. The idler gear mount is made from a good grade of cast iron, and the bearing surface is slightly hardened. The gear is made from cast steel which also machined beautifully.

Re: Got a 478...
 

Machining of the idler gear and the final product. After machining, the parts were cleaned and the bearing surface was coated with assembly lube to await installation.

Re: Got a 478...
 

Had the timing cover off to replace the sloppy timing chain on the 305. Also, replace the water pump and radiator hoses. Gave me a good opportunity to test fit the gear setup with the 305 timing cover. All fitted like a glove.

More to follow, hopefully soon enough.
Had to spend time on other projects but hope to continue the 478 these days.

Re: Got a 478...
 

Finally had time to continue the 478 build. I've completed the heads which have new valve guides on the exhaust side to accept the Cummins valves. Intakes were still fine regarding wear in the guides. Both exhaust and intake valves now have positive valve stem seals and were recut with a 3-angle valve job, with the intake having a 60 and 45-degree lead-in, followed by the 30-degree seat.
The exhaust has a 60-degree lead, 45-degree seat, and 30-degree exit cut. I used the specs in the book for the proper seat width.

I've ground off the "lip" from the Cummins valve to aid in airflow. I used the valve grinder to do this. See picture.

Finally, the heads could be assembled with freshened-up components. Then continuing the install of the cylinder heads on the block, followed by the valve train. I've set the cold lash to spec.

Before installing the assembled heads on the block I tested all the valves for leakage by spraying brake cleaner in the ports and checking for leaks. No leaks at all, so good to go. When cutting the seats, I coated them with a marker and turned the valve with a lapping stick to confirm the mating of the valve on the seat.

When installing the valve springs I noticed how little seat pressure the valve springs actually have. I might upgrade to stiffer springs later, but these will make for good break-in springs.

I will be painting the engine completely, but without the intake manifold so there will be good paint coverage on the valley cover and cylinder heads.
The intake manifold will be painted separately. The timing cover, water crossover, and oil pan will be borrowed from the 305.

In the picture, the intake manifold is not yet installed; just for mock-up.

Re: Got a 478...
 

Block is painted. According to Pete (BB V6) the blocks were painted in one go when the block was finished. I painted the block without the intake manifold in order to fully paint the intake manifold and valley cover area. VHT Ford red engine enamel (Duplicolor is the same) was used to paint the engine. 2 light coats of primer and 3 final layers of red. as you can see freeze plugs are only pushed in. Will change these out for new zinc-plated freeze plugs to add some contrast. Will see how it looks.

It really is pretty much identical to the GMC red, but the picture doesn't really show it due to the gloss. It still needs to fully bake when the engine is fired up. That will reduce most of the gloss.

Need to paint and install the last parts (e.g. dipstick tube)

The oil pan, timing cover, and water crossover will be taken from the 305.

Now to install the engine: SBCs use a plate with a lifting eye mounted to the intake carburetor bolts. Due to the weight of the V6, I don't really dare to do that. I figured to make 2 adapter plates that bolt to the cylinder heads, using the intake bolts.

Curious about what you used as mounting points to lift/install a V6?

Re: Got a 478...
 

Couple extra pictures. The stud is something you need to add when swapping the bigger V6 in a pickup, it bolts onto the pickup motor mount. On the truck V6's there is an oil retour (for the air compressor possibly?) I made one from an old oil galley plug which has a 7/16 UNF bolt plug welded to it. I shortened the plug so it was flush with the block.

The next picture is the bypass valve of my own design. it is set to open at about 14 psi and fits into the spin-on oil filter. It uses a plunger that gives room to 4 holes. The washers are shims to 'calibrate the pressure'. Due to the holes it opens and closes gradually and does not chatter on its seat. Hope it makes sense :)

Re: Got a 478...
 

More work done. Freeze plugs in. Had to see how those manifolds looked. Using the OEM steel exhaust gaskets. Still need to add the retainers but need to take those from the 305. Hope to park the GMC next week to start the engine swap among other things.

Coming along...

Re: Got a 478...
 

Starting to look like an engine again.

Re: Got a 478...
 

Another piece of the puzzle is the front pulley. I wrote about this in the 65 GMC build thread: I wanted to originally use the 478 pulley. However, it looks out of place, and it didn't fit after all. You would end up with an overdriven water pump as well.

Therefore modification of the 305 pulley is in order. I designed an adapter plate that can be used to bolt on external weights. It mounts onto the bolts holding the pulley in place, and nuts are used to fixture it. I am also working on a balancing fixture to determine the exact weight needed. The 478 pulley serves as a guide here.

Another 'upgrade' that I'm doing to the 305 pulley is the addition of the tapered sleeve, found in the bigger pulleys. This is a copper sleeve, that tightens onto the crankshaft when the front crankshaft bolt is tightened. It is easily added to the 305 pulley by machining a 15-degree taper into the bore.

More to follow.

Re: Got a 478...
 

Balancing fixture in action. I had to add a 2mm thick steel plate to the adapter. The 2mm plate followed the same contours as the underside of the adapter. As you can see, I had to remove as much material as seen in the picture to recreate the balance. I also had the timing indicator and adapter and weight zinc plated to recreate the factory look. All bolts were secured with LocTite and the front pulley was installed and torqued to spec. The tapered sleeve helps it stay rigid to the crankshaft, which is a worthwhile addition with the added weight.

Since we're nearing the end of the engine build the following posts will be continued in the 65 GMC build thread, where we install the engine.

Any comments are, of course, welcome :ok: