inline six woes

[Pops]

I have owned my truck for about 3 months. Having thoroughly read the "head gasket" thread, I felt I needed to start a different thread. That is, I couldn't find an answer to my problems.
So, I have a beautifully painted and clean engine and compartment (not show but very impressive). The motor doesn't sound bad and seems to be steady from a visual and sound appearance when standing in front of it. It doesn't hesitate once I get going, though, there is a slight vibration with clutch in and on initial take off. A few problems that I thought I should throw out there that may be explainable.
1.) The truck spays blackened liquid on most start-ups. I had to have the dizzy moved when I first got the truck as it couldn't be timed (vacuum advance was against block). This step helped lessen the carbon on the plugs and I was able to turn the mixture screw in about a quarter turn.
2.) The engine is not smooth if you feel the exhaust - erratic puff during idle.
3.) It burns rich, or incorrectly. Very few people tail-gate. I'm sure its the sulfury, acidic stench. The carb looks to be a re-manufactured Rochester one barrel; it responds well to mixture and idle turns.
4.) It doesn't seem to smoke at all while driving. Not even the condensation look. The only time I see any smoke (whitish blue-gray) is on start up. As I mentioned above, my muffler does seem to be holding water, or?
5.) I haven't ruled out head gasket but I would expect steam from exhaust if that were bad. Or, a milkiness in the oil.
6.) Timing marks on pulley don't match engine sound. The best I can get the engine to operate is when the pulley mark is on top of the pulley.
7.) Lastly, the prev-owner said to error on the side of rich when setting the carb. Not sure this was good advise as the plugs were coal black under his settings.

I don't like the vibration I feel when stopped at light. And I am bugged by exhaust smell. New plugs didn't help. :headscratch: If this sounds like your truck, and/or you know what the problem might be, please, please chime in. Thanks.

[quest]

I have owned my truck for about 3 months. Having thoroughly read the "head gasket" thread, I felt I needed to start a different thread. That is, I couldn't find an answer to my problems.
So, I have a beautifully painted and clean engine and compartment (not show but very impressive). The motor doesn't sound bad and seems to be steady from a visual and sound appearance when standing in front of it. It doesn't hesitate once I get going, though, there is a slight vibration with clutch in and on initial take off. A few problems that I thought I should throw out there that may be explainable.
1.) The truck spays blackened liquid on most start-ups. I had to have the dizzy moved when I first got the truck as it couldn't be timed (vacuum advance was against block). This step helped lessen the carbon on the plugs and I was able to turn the mixture screw in about a quarter turn.
2.) The engine is not smooth if you feel the exhaust - erratic puff during idle.
3.) It burns rich, or incorrectly. Very few people tail-gate. I'm sure its the sulfury, acidic stench. The carb looks to be a re-manufactured Rochester one barrel; it responds well to mixture and idle turns.
4.) It doesn't seem to smoke at all while driving. Not even the condensation look. The only time I see any smoke (whitish blue-gray) is on start up. As I mentioned above, my muffler does seem to be holding water, or?
5.) I haven't ruled out head gasket but I would expect steam from exhaust if that were bad. Or, a milkiness in the oil.
6.) Timing marks on pulley don't match engine sound. The best I can get the engine to operate is when the pulley mark is on top of the pulley.
7.) Lastly, the prev-owner said to error on the side of rich when setting the carb. Not sure this was good advise as the plugs were coal black under his settings.

I don't like the vibration I feel when stopped at light. And I am bugged by exhaust smell. New plugs didn't help. :headscratch: If this sounds like your truck, and/or you know what the problem might be, please, please chime in. Thanks.

Yeah, sounds like a tuning issue for the most part, do you have a vacuum gauge? You can easily find carb/ignition tuning instruction videos on youtube and probably even some for that engine!
If you can't get it fixed up that way then you want to check through everything for failing parts, the ignition system, plugs & wires, coil function, distributor functions, timing. Watch the engine run in the dark at night and make sure there is no arcing from any plug wires anywhere, then verify that your coil is putting out properly. Make sure each plug fires correctly. double check timing (location of #1) if you have relocated the distributor gear.
The last thing would be gas quality, make sure you have a clean filter and clean fresh gas. some vehicles have gas tank condensation problems due environmental factors, use some methyl hydrate(gas line antifreeze) in the tank if needed. Water/condensation in your fuel can cause what you describe here.

[Pops]

Thanks for taking time out to respond. To make sure I don't send advisers off on a goose chase, there are a couple more things worth mentioning:
1. I have a Petronix insert in distrib-- I know nothing about this product
2. I'm not sure how to test coil function. The friend who re-positioned the dizzy couldn't get #1 plug wire to spark off block. He didn't say why. Just said it should have.
3. All newer ignition parts on car; also gas tank, filters, etc. I have timed engine with light, and by ear. Still can't address smell, watery start-ups, or vibration at low RPM's while sitting at light. (and timing mark seems off when using light)
4. The truck came with a power brake booster add-on. Looks like it was meant for the truck - not custom. Do these create vacuum problems if not performing perfectly?
5. It sounds contradictory, but can turning the mixture screw more in counterclockwise direction actually address vibration. It would seem I was going backwards if i make it
more rich.

If I've thrown too much out there, please accept my apology. For now, could you please address coil function, and booster question. The PO had plugged off the vacuum line to booster saying he preferred the feeling of original non-power brakes. I changed booster grommet and put on new hose. I prefer power brakes by far. But, I am now a little suspect about why he really disabled the booster. I'm not throwing any stones right now, but I thought I'd share the last point so I'm not tearing up and replacing things when its in the vacuum system (at booster).

[quest]

Thanks for taking time out to respond. To make sure I don't send advisers off on a goose chase, there are a couple more things worth mentioning:
1. I have a Petronix insert in distrib-- I know nothing about this product
2. I'm not sure how to test coil function. The friend who re-positioned the dizzy couldn't get #1 plug wire to spark off block. He didn't say why. Just said it should have.
3. All newer ignition parts on car; also gas tank, filters, etc. I have timed engine with light, and by ear. Still can't address smell, watery start-ups, or vibration at low RPM's while sitting at light. (and timing mark seems off when using light)
4. The truck came with a power brake booster add-on. Looks like it was meant for the truck - not custom. Do these create vacuum problems if not performing perfectly?
5. It sounds contradictory, but can turning the mixture screw more in counterclockwise direction actually address vibration. It would seem I was going backwards if i make it
more rich.

If I've thrown too much out there, please accept my apology. For now, could you please address coil function, and booster question. The PO had plugged off the vacuum line to booster saying he preferred the feeling of original non-power brakes. I changed booster grommet and put on new hose. I prefer power brakes by far. But, I am now a little suspect about why he really disabled the booster. I'm not throwing any stones right now, but I thought I'd share the last point so I'm not tearing up and replacing things when its in the vacuum system (at booster).

I assume that dizzy means distributor and if you cant get #1 wire to spark then your vibration is coming from an engine mis-fire meaning that any wire that is not sparking properly is causing a that cylinder to "NOT FIRE", this will make the engine seem to vibrate or run rough!!!

If the timing mark does not seem to line up properly that is because it is not lining up properly due to the distributor rotor not lining up with your plug wire connections at the distributor.

Don't worry about the water coming out of the muffler or tail pipe it's just condensation.

I assume the petronix is an electronic ignition and it's my guess that this is ok or the engine would likely not be running at all.

You need to properly time the engine by hand. Get valve cover off pull out the number one plug and bring the engine to top dead center. Make sure the valves for number one are closed with a long lag time between valve movement(not the short lag time). Use a long thin screw driver in the plug hole or coat hanger to feel when the piston is positively at the top. Your timing mark should be at "0" now! If you have the piston and valves in the correct position then the rotor in your distributor should be lined up almost right at the #1 plug wire in the cap.

From what you have said I believe that it will not be close to #1. You should pull the distributor and get it lined up correctly or move your plug wires on the cap, keeping them in the correct order, to make them line up properly. You must still have enough swing room to move the distributor for timing adjustments.

If you want to do a poor man's test on the distributor/coil/plugwires then all you do is pull the plug wires off the plugs one at a time and put screwdriver into the plug wire while holding it with a glove on your hand. Bring the screw driver very close to any metal on the engine while running, or your friend turns the engine over and watch for a very bright spark(not a dull one), this is easier if it is a little dark out. If they all spark then all cylinders will fire and the engine should run smooth if your timing is correct. If one of them does not fire then you likely have a bad plug wire unless there is something going wrong with your petronix. If all seems to be ok after all this then start the engine and set your timing like usual, make double sure you put the plug wires in the correct firing order. If there is bright spark then you likely have a good coil.

I still recommend going to youtube to watch videos of using a vacuum gauge for tuning your carb, you will learn the most watching the video. disconnect and plug your brake booster vac line when doing this. you have to make sure there is nowhere to loose vacuum.

The bad smell is just un-burned fuel coming from the engine misfiring, that will go away when this issue is corrected. Making the carb run more rich will make that smell worse because there will just be more un-burned fuel.

Hope this gets you some good results

[turbobill]

Thanks for taking time out to respond. To make sure I don't send advisers off on a goose chase, there are a couple more things worth mentioning:

2. I'm not sure how to test coil function. The friend who re-positioned the dizzy couldn't get #1 plug wire to spark off block. He didn't say why. Just said it should have.

4. The truck came with a power brake booster add-on. Looks like it was meant for the truck - not custom. Do these create vacuum problems if not performing perfectly?

5. It sounds contradictory, but can turning the mixture screw more in counterclockwise direction actually address vibration. It would seem I was going backwards if i make it
more rich.

If I've thrown too much out there, please accept my apology. For now, could you please address coil function, and booster question. The PO had plugged off the vacuum line to booster saying he preferred the feeling of original non-power brakes. I changed booster grommet and put on new hose. I prefer power brakes by far. But, I am now a little suspect about why he really disabled the booster. I'm not throwing any stones right now, but I thought I'd share the last point so I'm not tearing up and replacing things when its in the vacuum system (at booster).


#2 Make sure spark is available at the plug from the wire. If not, the resulting skip will cause the problems you are having. (make sure the plug is good too)

#4 An internally leaking booster will cause enough of a vacuum leak to cause your idle quality problem. Leaks in the line/connections from the engine to the booster will do the same. To test, disconnect and plug at the engine connection first, then work toward the booster.

#5 Turning the idle mixture screw further counterclockwise MAY compensate for a vacuum leak depending on the leaks location and severity, provided the carburetor idle system has enough capacity to compensate.

[Pops]

Thanks a ton for advice. You guys are great!
So what I did today was set timing and mixture with vacuum gauge. Too easy, but, I felt it may be a more honest setting than using pulley mark. More than one person has said the pulleys wear on rotation components - giving incorrect reading. Made sense. Setting timing at max vacuum (with a little adjustment to steady vacuum needle) actually started the process of resetting everything. It lowered engine rev, vacuum called for leaner setting at carb, I set idle to 550. Today, I feel, improvements were evident. I'm not sure how to tell what the exhaust should sound like but it seems a little more balanced and a little cooler (rapbapbap). lol ..........Smell is still not great. Unburned gasses???

For other readers, I made a stethascope and aimed at all vacuum connections (booster, intake manifold, pcv, around carb, etc. All seemed good. I sprayed carb cleaner at intake gasket and idle did not change. Unless internal issue, I feel pretty sure I've done what I can from outside the engine.

It's a bitter sweet find, but I think the vibration is caused by u-joint problem.

Back to tuning, please share insight if you believe more is needed.

[GMCDAC]

Hi Pops, you said the vibration was occurring while stopped at a light? That couldn't be a U-joint as they would vibrate while moving. If I misunderstood, I apologize. A constant "poofing" out the tailpipe can be caused by a weak exhaust valve or seat. I am working on my '72 GMC and it had decent compression on #6 cylinder--125 psi(V-8) but was oil fouling plugs. I pulled a valve cover and ran it up to TDC on #6 to do a leak down and that valve was sitting an 1/8th inch higher than the intake. Valve seat was gone, but the valve was tuff enuff to kinda pound it's own seat into the head casting.

What Rochester one barrel do you have and what engine for that matter? There can be an issue with the power valve needle retainer spring if it is installed on the wrong side of the power piston arm with the Model M "MonoJet" carb. Drawings in the kits can be unclear and assume it was correctly built when they say to reassemble in reverse of dissassembly. I put the spring in the same position as it was installed on mine and it was running rich rough and smelly. Found out that a previous rebuild had put the spring on the bottom of the arm and I just assembled it as it came apart. Put the spring on top and it ran great.

I put a Pertronix in my 230 I-6 in 2011 and have not had any regrets.

DAC

[Pops]

Thanks Doug!
Your input is valued. As much evil as we find on the internet, its also an amazingly wonderful asset. I have gotten more information through guys like yourself than anyone else. Never need to apologize. I am still learning what to call things, and, sometimes I don't explain myself well enough.
I have two vibrations going on:
--One is sitting at light and engine is not silky smooth and therefore I feel and hear vibration transfer through cab. My mirror shimmies until I give it a little gas. This is part of the tuning I have been working on. Might add, its more of a vibration than rough running. (May easily be part of valve problem your are referring to.) To be honest, somedays the truck seems to run and smell a little differently. I sometimes want to blame my concerns on a watered down batch of gas, and/or the personality of the Rocheseter. I've also had times where a slightly richer setting helps with vibration.

--The second vibration feels like wheels out of balance between 10 and 35 mph. Whether going up in speed or coming down in speed. It just started doing this in the last month. My first inclination was tie rod components or ball joints as they are older and have deteriorated grease cups. It could be tire belts? But, yesterday I felt a clunk in rear on take off. This just started. Man at parts store said he would bet on u-joints.

Regarding the carburetor, I have a Model B if pictures tell the difference. I don't have a tag (remanufactured) but it does say BC on back side. I believe the "C" represents auto choke though mine is manual. I'm going to check fuel pressure soon as I have read that too much pressure will cause flooding; even leaking. My gasket at float bowl is always moist.

Better stop here or this will become a book - lol.
Have a great day.

[GMCDAC]

Thanks Doug!
Your input is valued. As much evil as we find on the internet, its also an amazingly wonderful asset. I have gotten more information through guys like yourself than anyone else. Never need to apologize. I am still learning what to call things, and, sometimes I don't explain myself well enough.
I have two vibrations going on:
--One is sitting at light and engine is not silky smooth and therefore I feel and hear vibration transfer through cab. My mirror shimmies until I give it a little gas. This is part of the tuning I have been working on. Might add, its more of a vibration than rough running. (May easily be part of valve problem your are referring to.) To be honest, somedays the truck seems to run and smell a little differently. I sometimes want to blame my concerns on a watered down batch of gas, and/or the personality of the Rocheseter. I've also had times where a slightly richer setting helps with vibration.

--The second vibration feels like wheels out of balance between 10 and 35 mph. Whether going up in speed or coming down in speed. It just started doing this in the last month. My first inclination was tie rod components or ball joints as they are older and have deteriorated grease cups. It could be tire belts? But, yesterday I felt a clunk in rear on take off. This just started. Man at parts store said he would bet on u-joints.

Regarding the carburetor, I have a Model B if pictures tell the difference. I don't have a tag (remanufactured) but it does say BC on back side. I believe the "C" represents auto choke though mine is manual. I'm going to check fuel pressure soon as I have read that too much pressure will cause flooding; even leaking. My gasket at float bowl is always moist.

Better stop here or this will become a book - lol.
Have a great day.

I also appreciate the help and education I get on this forum from the experienced folks posting here and hope to pay a little back now and then with some small things I have ran across trying to keep old beaters running on the cheap!-LOL!

Low volume flooding can cause exactly what you are describing, Pops. At idle small amounts of extra fuel will cause the rough idle but soon as more gas is required it will smooth out. The top bowl gasket will stay damp while idling quite often but may actually dry out off idle. The damp gasket is because the fuel bowl is too full possibly from a high float level or a damaged or worn out needle or seat or a float that doesn't float well anymore. If you have the mechanical fuel pump I really doubt it is over pressuring the needle, seat and pressure from the float unless there are the above described damage or wear.
There could also be debris stuck in the seat holding the needle open.
You probably know that the Model B is a dual float carb. They are great carbs and will last forever. I've got a couple and the only reason I went with the Model M is to get the "kick down" type manual choke. my B's require a throttle cable to keep the idle fast while opening the choke. I drive my '55 in pretty cold weather and like the high idle no choke warmup.

The clunk you described definitely sounds like a u-joint, and a bad one can cause vibrations at different speeds and load conditions.

Your carb may be one of these.

DAC

[Pops]

Yes Doug. I have the carb on the right. The fuel inlet is positioned high ;same side as mixture screw. I did remove the upper part of the carb to look at float. I removed float to check drop. Ok on that. I looked closely at float fit ; ok on that too. I did not go deeper into carb for I didnt have any backup parts or gaskets.
the carb looks newly rebuilt. (remanufactured). Wonder if I run cleaner through tank if that would help. I like techron but I see that other use seafoam. Also heard about drying additive to remove moisture. Any suggestions.I have long thought i have excess fuel prob.

Am I going to loose my drive shaft? Other than vibration and occasional 1st gear clunk, not hearing any red flags or urgent fix.

THANKS again Doug

Oh yea, I do have standard mechanical fuel pump.

[turbobill]

If a u-joint is causing a driveline virbration, don't ignore or neglect it. In addition to the vibration you feel, those same shock waves are raising havoc on other components such as the tailshaft bushing/bearing, pinion bearings and if equipped, carrier bearing and rubber.

Some will run a while that way, getting noticably worse, others will let go without warning, especially if the needles have fallen out. Sometimes, when they let go, there is much damage to other components attached to or nearby the driveshaft as the unrestrained end of the driveshft whips around

A friend of mine years ago lost a u-joint near the center of his box van (right behind the carrier bearing), the rear driveshaft dropped, dug into the pavement and catapulted the truck onto it's side. This was a larger box van approx 24,000 lbs GVW. His speed was 30 MPH.

My advice, get under the truck, check the u-joints and carrier bearing/rubber (if equipped) for looseness and repair whatever is loose or worn out. U-joints are cheap, relatively speaking.

[GMCDAC]

Yes! please take TurboBill's advice! a bad u-joint or carrier bearing can cause a lot of other damage.-

As far as an additive for fuel, put a clear plastic fuel filter on it temporarily to see if it loads up with debris and rust when you do that. I would change gas stations before I would buy a water remover additive if you suspect watered down gas. I do try to run ethanol free gas when possible. It ain't the same as the old gasahol from decades ago. the mixed stuff now is crappy quality and expensive for the quality of the product, but there isn't much can be done about it.

DAC

[Pops]

Hi Doug. Have you ever noticed that some guys will post over and over until they resolve their problem and then abruptly stop updating. That hurts.
That being said, I want to post until I'm out of the woods with I-6 woes. As you know, it helps to describe perfectly and consider air, fuel, and ignition when looking into performance probs.
For starters, I believe I was over-attempting to fix my engine bugs by leaning it out. It seems my engine wanted a bit more fuel. Secondly, vacuum leaks have to be addressed or nothing will ever smooth out. MOST all vacuum gaskets, hoses, valves, grommets were checked and replaced as needed. I am also now set up with a paper air cleaner instead of oil bath system (jury still out on this trial).
My latest find is a very faint hiss behind the booster; heard only inside the cab near the push rod. It takes a hose to hear it. It may be a normal sound; but I'm digging as I write. A bad booster usually gets a louder hiss as you depress the pedal; mine does not. However, if I'm not suppose to hear anything at all, then I need to get it right if I'm to move forward intelligently. Am I right? The engine needs to breath exactly as designed. As evidence to this, I disconnected the check valve while the engine was running and the truck stalled out. Hope this helps others.

[jagarra]

I think the best troubleshooting tool in this case is a minivac. I had a defective booster in one my vehicles, no symptoms at all, but a loss of vacuum. When I plugged the line going to booster and pumped up the system it held vacuum, with it connected it would not. Replaced booster and fine running again.

[Pops]

Thanks jagarra,
There are so so many variables to vibrations. WOW . Currently looking into a HEI or new flamethrower coil to go with Pertronix pointless set up. I've done mechanical corrections (all needed) like motor mount insulators, slip yoke, bal drive shaft, new u joints, new rear pinion seal, bearing and redi sleeve, etc. I have not ruled out carb at all. I looked down carb (not running of course), gave the linkage a decent push and did not see a straight stream of gas. It came out kinda weak and wand like with a couple extra drips. It's fine once it gets a higher volume of gas. Member Doug makes some good points on these one barrel Rochester B's. Some have suggested crank whip; others vacuum, etc. BTW, I will look into minivac check. Though I don't loose any pressure in pedal.
FYI, throw out bearing is another sore spot. That too can contribute to the effects i'm getting; I think??? They are worn, loose, incorrectly installed, etc. I can hear clutch or bearing friction when clutch is depressed. Also ticking noise if I depress top of clutch pedal (free play area) while driving.
LOL, this is an old thread revived. May get a resolution yet.

For other readers with inline woes, I did find carbon streaking in distributor cap on two towers. Also noted that the rotor was striking the inside of cap too high. It was grazing the plastic in the cap. Got rid of cap and went with a made in America heavier Borg Warner cap and new delco rotar. Plugs are cleaner and engine picked up power, Still have unburned fuel stink. Making progress!

[bobdylan]

I was having same problems on my Chevy 230 six, I was making it way to complicated, turns out the pvc valve was loose in the valve cover grommet, I wrapped some tape around it, ran fine.

[jimjaz]

I agree with Quest's comments- what does your timing mark say when #1 cylinder is at TDC? If it lines up at "zero", then good. If not, the timing gear chain may have jumped a tooth. Timing is everything...
- you should also be able to spark all of your plugs one at a time, if one is not firing, then this could explain the unburned gas you describe. BUT, running on 5 cylinders would be very noticeable.
- have you taken off the valve cover to see the valves in action at idle? You should see that they all are lifting about the same. A flat cam lobe will make your engine run like doo-doo, as you describe, but it will be "running" on all cylinders.
- have you done a compression check on the cylinders? This could reveal something. Do it "dry" first, then "wet" with a squirt of oil. If your valves and valve train are working properly, then a compression test "wet" will get you a higher number, if not, then the problem may be in the valve/valve train.
- the power brake booster; remove the vacuum hose from your carb manifold vacuum and plug it such that it does not leak, and take it for a spin. Maybe the booster is leaking internally allowing unwanted air into the engine? Not a common problem, but you may find something here.
- the carb; what is the history? If you bought the truck and it has always had the problems you are describing, this is worth investigating. I don't know anything about single-barrel Rochester carbs, but if there is something in your carb that does not belong, like a jet/metering rod that does not belong there. You might want to consider taking the carb off and paying somebody old-school who does this for a living go through it and rebuild it to factory specs. Probably will set you back about a bill-and-a-half. Carburetors can be a bit tricky, even single barrel ones.
I was battling a carb problem with the accelerator pump after it was rebuilt and came to find out that the leather cup (umbrella) was no longer being made, the replacement style was an O-ring on a detent acc pump shaft that was simply rolling itself off and dislodging itself, but this only caused me problems in starting it- once I got it running it ran fine, but getting it fired up was a real chore.

Hope this gives you some help along the way and gets you and your truck happily back on the road.

Cheers,
Jim

[TJ's GMC]

Just so everyone knows...Inline 6's do not have timing chains. They have gears. Some of them had a soft cam gear(I forget what material) that was prone for breaking teeth. Good upgrade would be aluminum gears.

[GMCDAC]

To add to TJ's comment, he is right on about the timing gears. Here's what can happen to the composite cam gear. I bought a '64 Chevy pickup for parts non-running and this is why it didn't run. This engine is a 250. The 230 in my '55 GMC has the aluminum gear. It makes a bit of a whine, but that's better than having the issue this 250 has!

DAC

[TJ's GMC]

To add to TJ's comment, he is right on about the timing gears. Here's what can happen to the composite cam gear. I bought a '64 Chevy pickup for parts non-running and this is why it didn't run. This engine is a 250. The 230 in my '55 GMC has the aluminum gear. It makes a bit of a whine, but that's better than having the issue this 250 has!

DAC

That will cause some problems. lol

[Pops]

Wow, it's been a long, long time. This was such a lengthy post I thought I'd take a minute and share what I did and what the status is now.
Misfires, shaky steering wheel on take off, vibration, whining noise, etc. are partially corrected.
Whining was related to rear end (of course). the seal at pinion was shot. The tiny spring around the seal was spun and broke. While removed, I also had the bearing changed (easy and cheap at that point) it was weak. also put a redi sleeve added to assure no more leak. Bal drive shaft and added u-joints. NO more noise.
Still have shakiness on take off; pretty smooth after that. exhaust is still stinky which leads me to think carb (rochester B). GMCDAC wrote about this. I have a remanned carb but that doesnt guarantee anything. Im wondering if the seal around mixture screw is crushed. When I set the carb it only requires about 1/4 turn to satisfy vacuum and idle. I was told if the inner seal is crushed it will probably run rich. Since my plugs carbon up quickly it sounds like a rich running engine.
Doug do you sell Roch 250? Esp rebuilt by you? If so, what is the process?

[TJ's GMC]

Yeah the rochesters are junk, I tried rebuilding two and still had rich running or flooding issues. I got lucky with the reman I purchased for one of my 292's. It's a monojet 1 barrel. No issues thus far. I dumped the rochester on one of my 292's for an eddy 4 barrel. lol!

If you still have issues a common upgrade is the weber 32/36 2 barrel. Kind of a pain to tune, but you will get a nice mileage increase and a little increase in power once tuned. :thumbsup:

[turbobill]

Yeah the rochesters are junk,

No they aren't. People say the same thing about Q-Jets.

Just have to know what you're doing.

[TJ's GMC]

No they aren't. People say the same thing about Q-Jets.

Just have to know what you're doing.

Might need to have a pro do one of mine then. Last rebuild I did I cleaned and replaced and set everything to stock specs. Still had problems, Ran much better than before though! Acted like it had a vacuum leak some where....had some hesitation when given throttle, couldn't find the leak. Replaced with a small 4 barrel and headers and never had any hesitation issues again. :teehee:

Forgot to mention, I did not mean ALL are junk, just that particular line. All 3 of my 6's had problems with them, and all of us 250 and 292 enthusiasts have had the same common issues.

[GMCDAC]

I have had good luck with the Rochesters, the only reason I went from the Model B that was on my '55 GMC (mid 1960's 230 Chevy engine) was to get the "kick down" fast idle with the choke cable. I got 3 parted out Rochester Model M carbs and was able to build one out of the three.

Pops, the Model B I sold to a member on this site came from a '64 Chevy truck I parted out. I didn't build it but the carb had a fairly fresh rebuild. I put it on my 230 for awhile and it ran well. It sounds like it worked ok for the buyer. No I don't build carbs for anyone but myself.

DAC

[Pops]

thanks for feedback. I would prefer the Roch because linkage, air cleaner, man choke would all work. But, I am pretty much fed up wtih rich burn, exhaust smell, and mileage. and slight shaky on take off. I agree it acts like vacuum leak. Which opens up another posibility. My booster is a cardone with a 67 dual barrel master. I replaced check valve - no change. I sprayed around carb - no change. I change pcv - no change. I ran vacuum test and got a pretty steady needle +- 17 pnds. So I am back to carb which leaks at upper gasket around bowl.
Tj, why is weber 3236 diff to tune. and, does linkage and man choke need to be reorganized?

[TJ's GMC]

Tj, why is weber 3236 diff to tune. and, does linkage and man choke need to be reorganized?

Jetting and fine tuning was the main pain for the last read up I did on it. Linkage I believe has to be redone, choke cable would be a matter of lengthening if needed. I'll search for the write up on it, been a year or so. lol Most of us convert to 4 barrels, but there are a few that convert to webers or holley 2 barrel carbs.