It just will not run right - Pontiac GTO Forum
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post #1 of 25 (permalink) Old 05-14-2017, 10:36 PM Thread Starter
 
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It just will not run right

66 Tripower, fresh 10 years ago but never started. Fired it up and broke the cam in. only runs on 2,4,6 and 7. Other cylinders getting spark but appear to over fuel. (plugs wet, pyro temps 150 degrees) no change with plug wire pulled. compression test lowest 195, highest 225, cold cranked. intake vacuum 10"hg. replace intake and went to single carb. Same results. replaced distributer, cap, rotor, wires. verified spark plugs at .035. Dwell at 30. swapped out coil. good fuel pressure and needle and seat holds it. Checked valve lash (hydraulic), correct.verified spark at plugs too. Basically all the parts including the tripower and carbs, dist., carb, wires, coil, etc. are all new (not to say something new isn't bad)
wouldn't think the timing gears could be off since it actually runs very strong with only 4 holes firing good. I guess the next step, even though it is fresh is to tear it down and start over. Suggestions?

1964 400 4 speed Roller cammed RoadRacer
1969 400 T400 auto 2nd owner
2004 LS1 6 speed modded for roadracing
1966 GTO Altered wheelbase former 1970s show car
1973 Challenger 360/727
1931 Ford Model A

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post #2 of 25 (permalink) Old 05-15-2017, 09:16 AM
 
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First re-verify firing order, check and be sure.

Next, compression on left side 1,3,5,7 must be right and rockers and springs must be working right. Could the push rods or lifters be hanging up?

Remove the valve covers and plug the rockers with those little wire things all the auto parts houses sell so the oil doesn't shoot everywhere, and watch the rocker arm assembly when it is running....see if rockers are moving as suppossed to or hanging up...

A leakdown test on each cylinder might be a good idea as well, as a bad head gasket or intake manifold gasket put in the wrong way on that side could be causing the the mixture to be too lean and won't fire.

Smoke test can find that,....but if you have had that intake on and off with the tri-power that would be a place to suspect.....

Bad left intake gasket or head gasket

Hang in there you will get it!
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post #3 of 25 (permalink) Old 05-15-2017, 09:22 AM
 
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PS 64 a no firing condition, if from a lean mixture as I described will make the plugs wet as the fuel does not fire....it seems counterintuitive that a lean condition causes wet plugs,

but just possibly your lean condition causes no fire at all and all the unburned fuel remains in the left bank of cylinders..so check those gaskets, if you have lived a good life it may be the intake gasket!
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post #4 of 25 (permalink) Old 05-15-2017, 06:08 PM
 
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Hmmm. New one on me.

Do you have a good ground between your frame/engine and engine/body? Could be as simple as poor grounding affecting the plugs.

Noticed your vacuum is not all that good at 10", but may be because only one side is firing. I would be looking for a vacuum leak on that side - to include the hose going to your power brake booster if you have one. Spray a little carb cleaner around gaskets/carb to see if the engine speeds up.

Read on one post that the problem was a collapsed exhaust pipe on the side that was having all the issues. The stock exhaust manifolds had an exhaust "butterfly" to route exhaust gas under the intake and as the engine warmed, a bi-metal spring would unwind and the butterfly would go to its full open position. If a car sits, these things will freeze up closed on you. So check for this as well as put your hand on the tail pipes to see if you fee the same amount of flow.

I would also put in a new set of plugs as once they get wet, even though you clean 'em, you can have problems.

As suggested by Lg, pull the rocker arm cover on the bad side. Check the valves. You might have them too tight and they are not closing. I know that sometimes people are given Chevy lifters which will not work in a Pontiac - oil band in the wrong place and you won't get any oil to the rocker arms. I don't know if it would cause any issues with keeping the valves slightly open once they pump up after they are running.

It is possible that the head was milled on that one side and the rocker arm geometry is now off - pushrods too long and keeping your valves open slightly.

Distributor- what type? Points or electronic? Rebuilt or original? If original points, bushings could be worn, condensor weak/bad, poorly grounded, vacuum advance can not working correctly or sticking. Are you running the engine with the vacuum line to the vacuum advance unplugged? Try that to see if it does anything.

Try a few of these suggestions and then let us know. Just seems odd that it affects only 1 bank.
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post #5 of 25 (permalink) Old 05-15-2017, 10:57 PM Thread Starter
 
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thanks guys. It affects both banks. 1,3,5 and 8 don't fire. When I first looked at the valve train it had store bought washers under poly locks with stock studs(lol). I pulled all of them, checked that valve height was all the same on each head and installed stock nuts minus the washers. I watched each one go to zero(with the push rod cover off) and as I went to zero lash they depressed the lifter and locked at 3/4 turn. So all good there. As far as the distributer the stock rebuilt numbers one is points and perfect BUT, I swapped it out with one i have that is from one of my race cars. It is only mechanically curved and has points. Also changed the cap, rotor and wires to be sure. As fas as plugs go I put the plugs from the non-firing cylinders into the firing cylinders and it runs the same. I also replaced the intake gaskets along with installing a 1967 square bore iron pontiac intake plus a AFB that came off my '73 Challenger when I put it back to Stock. The Challenger ran perfect with it. So I guess what I am saying is ANYTHING that was a variable or suspect I replaced with proven parts and get the same result. Only thing that caught my attention was when I was installing the intake it was difficult at first to get the bolts to align because I think the block may have been decked a little. I have a fresh '67 XH that was decked to zero and it has its own iron intake and NOTHING else fits it, so I am starting to lean that way. When I pulled the tri-power the gaskets were wet at the bottom, but that can come from disassembling too. I think the next thing to do is pull the intake and set it on minus the gasket and measure the clearance across the gasket area. in answer to valves being open there is no backfire or exhaust pop to indicate sticking or partially open valves. Your right Jim, I will get it, I've been building Pontiacs since 1978 so I feel I know them.

1964 400 4 speed Roller cammed RoadRacer
1969 400 T400 auto 2nd owner
2004 LS1 6 speed modded for roadracing
1966 GTO Altered wheelbase former 1970s show car
1973 Challenger 360/727
1931 Ford Model A

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post #6 of 25 (permalink) Old 05-16-2017, 12:15 PM
 
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Interesting that with one exception the cyls that don't fire are together in the firing order. But since you swapped dizzys I doubt that has anything to do with anything. Have you verified spark at each of these cylinders?
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post #7 of 25 (permalink) Old 05-16-2017, 04:44 PM
 
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Sorry about that I read 135 and put the 8 in myself, I think you are on the right track. When you changed Dist did you change the cap and rotor as well? It can be done either way...if you were using the same ones I would suspect a cracked Dist cap, which can give that odd failure to fire.

I don't know if you have access to a scope, or even a spark KV tester, cylinders can spark, but the spark is weak and won't fire the cylinder...if you do it by visual alone you see spark, but that spark is not under compression where it needs more kv to fire, ......

It is an odd set, crossfiring wires, weak KV, cracked Dist cap...if the problem is ignition. Fuel problem can be what you are searching for on the engine, if the deck cut lets air in to screw up the fuel air mixture....

Anyway, pulling for you sure you will get it!
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post #8 of 25 (permalink) Old 05-16-2017, 05:19 PM
 
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If you had the deck zero milled (about .020") and the heads trimmed a bit, could be some misalignment with the intake - so your intake may indeed not be sitting squarely at the base and is why the gaskets were wet with gas on the bottom. The intake bolts should fit fairly easily. So you most likely need to have the intake cut down since you won't be pulling the heads and milling them. Could be a gasket matching problem or not seating correctly.

If you have "stock studs," assume you are talking about press-in studs. Using stock nuts, and not the polylocks, they need to be torqued in place. You cannot use the stock nuts to zero lash the valvetrain - that's where polylocks are used. The stock nuts will eventually back off.

Second, with the deck zero milled and the heads most likely milled, your pushrods are most likely too long and again, may be holding open the valves. I would confirm the pushrod length using a pushrod checking tool. All the info on how to check it is here and you can get the one you need: http://www.compcams.com/catalog/COMP...12_292-311.pdf

"I also replaced the intake gaskets along with installing a 1967 square bore iron pontiac intake plus a AFB"

You could have a mismatch between the carb/intake. Some of the original AFB's were only about 500CFM's and smaller in size. The later AFB's may have a larger base and could be hanging over exposing vacuum ports or even the throttle blades. If you have the 750 CFM, it has the larger secondaries which may not open on the smaller Pontiac AFB. Did you verify the fit and correct matching gasket? Could be sucking air.

Hang in there and keep checking things. Gotta eventually figure it out.
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post #9 of 25 (permalink) Old 05-16-2017, 07:38 PM Thread Starter
 
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Originally Posted by 64GTOConvertible View Post
Interesting that with one exception the cyls that don't fire are together in the firing order. But since you swapped dizzys I doubt that has anything to do with anything. Have you verified spark at each of these cylinders?
Yes and put the non-firing plugs into the hot cylinders...same result

1964 400 4 speed Roller cammed RoadRacer
1969 400 T400 auto 2nd owner
2004 LS1 6 speed modded for roadracing
1966 GTO Altered wheelbase former 1970s show car
1973 Challenger 360/727
1931 Ford Model A
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post #10 of 25 (permalink) Old 05-16-2017, 07:49 PM Thread Starter
 
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Originally Posted by PontiacJim View Post
If you had the deck zero milled (about .020") and the heads trimmed a bit, could be some misalignment with the intake - so your intake may indeed not be sitting squarely at the base and is why the gaskets were wet with gas on the bottom. The intake bolts should fit fairly easily. So you most likely need to have the intake cut down since you won't be pulling the heads and milling them. Could be a gasket matching problem or not seating correctly.

If you have "stock studs," assume you are talking about press-in studs. Using stock nuts, and not the polylocks, they need to be torqued in place. You cannot use the stock nuts to zero lash the valvetrain - that's where polylocks are used. The stock nuts will eventually back off.

Second, with the deck zero milled and the heads most likely milled, your pushrods are most likely too long and again, may be holding open the valves. I would confirm the pushrod length using a pushrod checking tool. All the info on how to check it is here and you can get the one you need: http://www.compcams.com/catalog/COMP...12_292-311.pdf

"I also replaced the intake gaskets along with installing a 1967 square bore iron pontiac intake plus a AFB"

You could have a mismatch between the carb/intake. Some of the original AFB's were only about 500CFM's and smaller in size. The later AFB's may have a larger base and could be hanging over exposing vacuum ports or even the throttle blades. If you have the 750 CFM, it has the larger secondaries which may not open on the smaller Pontiac AFB. Did you verify the fit and correct matching gasket? Could be sucking air.

Hang in there and keep checking things. Gotta eventually figure it out.
What i meant to say was I used stock Pontiac rocker nuts and turned them down to zero lash. Then each one went 3/4-1 turn to torque so the pushrods and train should be correct.I have a length checker since I built my roller for my 64.
Carb and intake match plus it ran the same with the tri-power set up, same dead holes, etc. I have eliminated all the variables items it seems. I think I need to compare intake, head angles.

1964 400 4 speed Roller cammed RoadRacer
1969 400 T400 auto 2nd owner
2004 LS1 6 speed modded for roadracing
1966 GTO Altered wheelbase former 1970s show car
1973 Challenger 360/727
1931 Ford Model A
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