Left side of engine not smooth like right

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tusharriv
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Location: Noblesville, IN

Left side of engine not smooth like right

Post by tusharriv »

Hello everyone. I have been spending the last 18 months trying to chase down all of the gremlins in the engine of my 67 Convertible with a 110 and a PG. The carbs have been rebuilt, Crane electronic ignition installed, new fuel pump, new wires, new coil, new fan bearing, all o rings replaced, fins deflashed, and more. It went from an engine that wouldn't get me 35 miles without overheating to one that I can confidently drive around here for an entire day without too much trouble.

I have one more think I am trying to figure out. Since i purchased the car, the left side of the engine has always seemed to be a bit more problematic than the right. I installed a duel exhaust about a year ago, and since then, it has become more evident. While the right side is smooth and consistent with the exhaust from the tail pipe, the left side will have sporadic skips and what seems like larger puffs of air coming out. This seems to happen much more when the car is at idle instead of drive. In fact, last night I was checking it again, and in drive I could put my hand at the exhaust, and it would feel just like the right side. It drove nice last night with no problems like usual. When I put it in neutral, it immediately started that inconsistent exhaust and puffing on the left with the right being smooth. Since I have had the car, I can see this on the timing light with it jumping around a little bit. It can get especially bad even when driving, and can become very easy to hear and feel when stopped at lights. It is very inconsistent with how bad it will be on a given drive. I have checked the vacuum. The harmonic balancer was replaced with a rebuilt one, but I can't promise that it is perfect. Compression has been good, and it does not eat oil at all. So, what else can I look at? I would think it might be the valve adjustment, but it was been adjusted both by myself and a professional with the same results. A buddy told me that a valve seat could be starting to go. I hope that isn't it. Any ideas or suggestions are appreciated.
Tony Rivera
1967 Corvair Monza Convertible 110 PG
Noblesville, IN
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Re: Left side of engine not smooth like right

Post by terribleted »

This is usually caused by a valve issue or an ignition issue. Sticking valves, loose seat, or valves adjusted just a little too tightly (holding open now and again) can cause this spitting as can misses in the ignition system from intermittent spark. Could also be caused by detonation caused by hot spots from carbon buildup in that head. Another possibility is carb issues.

What to do. I would do these in order. Replace the sparkplugs (cheap enough) just to make sure it is not some intermittent plug issue. Try swapping carbs and see if the issue follows the carbs. If the issue follows the carb...disassemble and find the issue in the now right carburetor. Re-adjust the valves running, and whatever pre-load you are currently using I would try maybe 1/8-1/4 turn less (in any case do not adjust to less than 3/8 of a turn in from quiet during running adjustment).
Corvair guy since 1982. I have personally restored at least 20 Vairs, many of them restored ground up.
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azdave
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Re: Left side of engine not smooth like right

Post by azdave »

tusharriv wrote: Thu Aug 31, 2017 5:33 am A buddy told me that a valve seat could be starting to go. I hope that isn't it. Any ideas or suggestions are appreciated.
If a valve seat was the issue then why would you have good compression? A bad valve seat would not be okay for a while and then bad again later. You said the issue comes and goes correct?

My guesses are ignition or carb issues. A common trick to see if you have a carb issue is to swap the carbs from side to side and see if the problem moves to the other side. Do you have similar airflow through each carb at idle and off-idle? Did you perform a through carb linkage/airflow balance after all the repairs? Check really closely for vacuum leaks too. Is your PCV system in place? Has anyone before you drilled out or removed the metering orifice (which could essentially be a big vacuum leak).

I've never used the Crane ignition but I know the Pertronix II's sometimes have issues at low idle conditions, especially PG cars. Many people will go back to using their old ignition points to test if a new ignition system is not up to the task. Just because it's new and supposed to be better doesn't always mean it is. Test against known good parts.

A bad harmonic balancer might cause you to mis-read the timing numbers but it isn't going to cause an intermittent miss or engine stumble. There are alignment reference marks between the HB inner and outer pieces. See image. If those marks don't align then you'll know the outer ring has slipped.
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HB old.JPG
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gnrand
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Re: Left side of engine not smooth like right

Post by gnrand »

Maybe check the Ohm reading on your spark plug wires to see if one has high resistance.
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tusharriv
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Re: Left side of engine not smooth like right

Post by tusharriv »

Thanks for the ideas. I did replace the plugs not all that long ago with original AC plugs, and it didn't make a difference on the stumbling. It did seem to make my engine run a bit smoother overall though.

The Crane was one of the first things I put on the car right when I got it, so it might be worth throwing some points back in to see if that resolves the issue at all. I will also swap the carbs to see if that does anything. I believe the vacuum system is in good working order, but I will check it once again. Is there a surefire way to check the vacuum system?

I will try to adjust the valves again, but I have such a difficult time hearing when doing a running valve adjustment. Is there a better way to do that with the muffler off that still allows you to hear something?

Is there anything that really works well for cleaning out the carbon in the engine without messing it up. I know some people use seafoam, but I don't want to just throw snakeoil into it that won't do anything.

Thanks again!
Tony Rivera
1967 Corvair Monza Convertible 110 PG
Noblesville, IN
gregpenn
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Re: Left side of engine not smooth like right

Post by gregpenn »

On my 140hp the left exhaust assembly broke off. Before I repaired it I noticed when it was idling there was no noise because most all the exhaust was going through the right muffler. Only when I accelerated did exhaust flow from the left side creating the noise of exhaust with no muffler. The engine does have a miss at 35-40mph that one mechanic said he thought was related to one of the 4 carbs. ??

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Re: Left side of engine not smooth like right

Post by bbodie52 »

:think: Your description of the work that you have accomplished replaced or upgraded much of the ignition system. You did not mention, however, whether or not you replaced the distributor cap and rotor. A faulty distributor cap could potentially introduce misfiring in one or more cylinders, if you have carbon tracks or other internal damage in the cap.

As previously mentioned, a valid compression test on each cylinder should identify any mechanical faults in a cylinder, such as a leaky head gasket, faulty valve seat or valve, bad piston rings, etc. If your compression on all cylinders is even (approximately 130 psi the maximum variation of 20 psi between cylinders) you can probably eliminate a mechanical fault or valve problem from your list of possibilities. That pretty much leaves fuel system or ignition system as a source of your problem. On the ignition side of the equation, spark plugs, spark plug wires, and a faulty distributor cap would normally be the only things that could consistently introduce a problem on one side only. I can't imagine anything in the ignition coil or electronic ignition system that would introduce a problem on one side only. Reading the spark plugs (comparing their appearance) might reveal an individual cylinder that is burning differently than the rest, or a group of cylinders on the left that are burning differently than those on the right.

If the ignition system is sound, and if the engine is mechanically sound, the only thing left would be the carburetor or possibly a vacuum leak from some source on the left side only. A vacuum gauge connected to one side, and then the other might reveal differences in the manifold vacuum. A vacuum leak can be introduced by a split hose connecting the balance tube to the intake manifold. A cracked insulator at the base of the left carburetor could also introduce a vacuum leak that is not readily apparent. As previously recommended, swapping the left and right carburetors to see if the uneven operation follows the carburetor or remains on the left side would at least help you to eliminate the carburetor is a source of the problem. Have you tried measuring the airflow through each carburetor with a Uni-syn gauge? This would help you to confirm that the left and right carburetors are in sync, both at idle and that part throttle.

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Brad Bodie
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Re: Left side of engine not smooth like right

Post by terribleted »

After re-reading your original post. I am betting that the problem will swap sides when you swap the carbs we will see.


I always adjust the valves with exhaust in place. I keep and old set of basic dual exhausts to install when I need them as well for just this purpose. Duals swung down under the oil pan is best, but I have adjusted around most exhaust systems as well. Headers are tough because of noise as it is little hard to hear the lifter go quiet.

Carbon buildup is a low probability issue. I bet you will find your issue before you have to think about this. I have only seen this a couple times in years and in both sides.
Corvair guy since 1982. I have personally restored at least 20 Vairs, many of them restored ground up.
Currently working full time repairing Corvairs and restoring old cars.
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