Engine Troubles... Please Help

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91blaze
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Engine Troubles... Please Help

Post by 91blaze »

Please read this entirely! I have done a lot of troubleshooting and it will save a lot of repeat information.

Alright everybody, I'm finally at my wits end and throwing in the towel on this one. My car has not been running right for a few weeks now and I've spent countless hours troubleshooting. It did great running to and from Pittsburgh from Indianapolis, even doing 75 mph the whole way back. A few weeks later though it suddenly had issues idling and running over 3k rpm. I do drive this car 80+ miles a day so I know it's not from sitting. I took the carburetors apart and cleaned them thoroughly (these were purchased from Wolf at the Knoxville convention so gaskets and parts are not very old). This helped the idle issue but not much else. Yes, carbs were synced and idle screws adjusted properly.

Next I replaced the distributor (still running the original and needed the excuse to finally get one of Seth's with HEI plug wires). I was now able to run over 3k but only at certain throttle positions and still has misfiring when cruising at or above 3k rpms. I pulled the plugs which were a bit old and put in new Bosch WR8AC plugs with 0.040 gap. New high performance coil put in just to be sure. I checked engine ground resistance with a meter and it was good. I put a relay going to the coil to ensure full voltage there. Timing was advanced until it pinged under load and backed off a few degrees.

Please note that this all occurred over the last few weeks and I did test drive after every change. It still has an erratic misfire while cruising over 3k rpms (about 60+ mph) and will stumble at full throttle. I can get up to normal rpm's at about 85% throttle. I pulled #1 plug after driving a day and it was dark so I know it's running rich (not oil soaked). The old plugs I pulled were also dark.

The last major change I could make is new carburetors but I really don't want to spend the money if there are other things to check. Just FYI, I have a 110 with headers and running #54 jets, everything else stock other than the ignition system. As I said before, it was running great up until a few weeks ago when it suddenly started running poorly. Also, I was getting low 20's average fuel mileage before but now getting under 15 so I know something is majorly wrong here. Please help me before I lose my mind!
Last edited by 91blaze on Thu Sep 06, 2018 5:50 am, edited 1 time in total.
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terribleted
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Re: Engine Troubles... Please Help

Post by terribleted »

Sounds like it is rich. 54 jets are pretty big. I have never seen any reason to run larger than 52's. Are you sure it is not flooding at all? Start engine and run a couple minutes with the air cleaner removed. Shut it down and look for any dripping in the carb throats which would indicate fuel pressure getting past the needle valves (flooding). If the plugs are black they may be delivering a somewhat weak spark which will be most noticeable under demand at higher rpm's. How were the adjustments in the carbs? I am sure you did all the adjustment procedures from the shop manual while you had them off and apart for cleaning right? Why a 40 gap? Sounds a little big, but, not sure it is too big for the ignition being used. What is the timing set at? best not to run more than around 17-18 degrees even if no ping is noticed. Is the car a stick or automatic?
Corvair guy since 1982. I have personally restored at least 20 Vairs, many of them restored ground up.
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91blaze
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Re: Engine Troubles... Please Help

Post by 91blaze »

The plug gap was from what some suggested was able to be ran with the HEI and high output coil. I've been running 54s for a year now so I doubt that is the issue. I do have 52s I could put in but that wouldn't account for a nearly 10mpg drop. I did the carb adjustments running as I've always done and synchronized them while running as well. It idles well and will run fine under moderate acceleration. Even running 65 mph I can increase the throttle and the misfire goes away unless I go to the floor with it. Full throttle is the worst misfiring and it just falls flat. I can drive it 75 on the interstate but there is a very noticeable misfire. It is a stick and I don't have an exact number on the timing but it's right about where it was before this started. I can't advance any more without pinging and retarding just worsens the problem. I will run it with the cleaner off this evening to see if maybe there is dripping but it doesn't make sense why it would suddenly do this after putting several thousand miles on it just this year.
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65Ragtop
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Re: Engine Troubles... Please Help

Post by 65Ragtop »

1.Do you still have the same tank of gas that you had when the first trouble started?....Sometimes its as simple as some bad gas, it happens now and then.
2. Vacuum leak someplace either full on or intermittent? Checked all your hoses, base gaskets and pipes?
3. Clogged or clogging fuel filter either in the carbs (brass) or sometimes an aftermarket one can be found in driver side rear wheel well.
Just some thoughts. Hope you figure it out.
Mike S.
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91blaze
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Re: Engine Troubles... Please Help

Post by 91blaze »

1. I've been through several tanks since it started, this crappy mileage isn't helping.

2. All replaced withing the last year or two, nothing noticeable when I checked everything. Choke pull off hoses came with the rebuilt carbs but I may replace them to be sure.

3. Seems to be getting too much fuel, not starving. I did check the brass filters when I cleaned the carbs and they're good.
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Re: Engine Troubles... Please Help

Post by bbodie52 »

Image :vert:


:think: :confused: Have you recently performed a compression check on all cylinders to make sure that a mechanical flaw has not developed?


Is fuel pump pressure and volume within specs? :Potty:


:wrench: Checked carburetor float level and checked floats to confirm that the floats have not developed a leak (gasoline inside a float) that could produce fuel level problems in the float bowl(s)? This could produce a rich-running engine.

Do the spark plug readings (appearance) appear to be equal on both cylinder banks?Image :pray:
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Re: Engine Troubles... Please Help

Post by Flying_Dan »

Get a differential gauge and do a leak down test. It sounds like something happened mechanically as stated.
When I set my timing, why to a flush, then pee?
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Re: Engine Troubles... Please Help

Post by terribleted »

You say the timing is in the same place it was before this started. That would mean it is set the same as before you changed the distributor? Put a timing light on it and see where it is actually set. A compression test would not be a bad idea either, just to make sure there is not some other engine or valve train issue that may be influencing the situation. You say advancing the timing more just makes it worse. I am stating that you may have too much advance...PUT A LIGHT on it and see where it actually is timed.
Last edited by terribleted on Wed Sep 05, 2018 9:41 am, edited 1 time in total.
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martyscarr
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Re: Engine Troubles... Please Help

Post by martyscarr »

Like Brad suggests, I would do a compression test.

Does this engine have a lot of miles on it? Given your symptoms, I think I would put the engine on #1 TDC and drop the oil pan, and check that the cam timing mark is at the case halves. Several of your symptoms suggest a sheared key in the crank or cam gear, and you've already checked the usual suspects.
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91blaze
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Re: Engine Troubles... Please Help

Post by 91blaze »

Floats were fine when I pulled carbs apart, no sloshing inside. Pump doesn't show any signs of leakage and appears to be working normally. Not sure how bad compression on one or two cylinders could cause all the plugs to read rich but I guess I can check that when I have time. I have all the normal power at lower rpms and it's perfectly drivable until I get to highway cruising speeds or try to go full throttle at high rpms. I'm leaning towards carburetor issues at this point. Won't be able to do any major checks like compression until tomorrow evening as I'm not going to be home until late tonight. Appreciate the suggestions guys, keep it coming.
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Re: Engine Troubles... Please Help

Post by terribleted »

Compression test is not likely to show an issue, BUT, it is easy to do and if it does it can save you headaches looking in other places. Making sure the timing is at or close to spec is also very easy to do and actually could be an issue to cause your problems as could flooding. Always do the simple things first and move to harder more involved troubleshooting when those areas a known good.
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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91blaze
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Re: Engine Troubles... Please Help

Post by 91blaze »

Ted, please see before where I said retarding the timing made it misfire more. Advancing more causes pinging, not misfiring. This is the same manner in which I set the timing normally, advance until it causes detonation then back it off.

Marty, it has about 150k on it currently. I would think a problem as major as you suggest would cause problems throughout the rpm band, not just at specific parts.
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Re: Engine Troubles... Please Help

Post by 66vairguy »

Terrible Ted's advice is good. First the Seth distributor uses an external coil. There were issues for awhile with some coils and Seth has narrowed the list to those that work well. Not knowing what coil you have I would first regap new plugs to 0.035". You will still get a more than adequate spark and eliminates a possible under powered coil issue. BTW the Seth dist. usually runs a coil wired directly to 12VDC ignition power, no ballast (resistance wire in Corvair engine harness).

Carb Jets - I know a lot of folks are convinced going up a couple sizes is needed with air cooled eingines, but my experience is that I find a lot of carbon in the heads, stuck rings, etc. You are driving this car a lot daily, not racing it. Go back to the 52's. I run them in my 140HP and get high 20's MPG on the highway and the plugs look great. No pinging either and I drive in the hot S.W.
Carburetors can be tricky and even vendor rebuilts have issues. I rebuild my own and sometimes you just get a bad carburetor that looks fine but will not work possibly due to being warped or having internal passage leaks. It's a lot of work, but sometimes you have to find another carburetor, or pair, to determine if fuel is the issue.

Timing. In the last couple of months two guys in our club had bizarre running issues. One was a broken harmonic damper (timing mark moving) and the other found his new Seth distributor was slipping so the timing was changing (I think he left the dist to block gasket out).

You said your engine has 150K miles on it. While not common - sometimes the cam or crank gear shears the woodruff key and slips. This changes the cam and distributor timing with relationship to the crank and obviously the engine will not run well. Difficult to check.

Good luck.
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Re: Engine Troubles... Please Help

Post by martyscarr »

91blaze wrote: Wed Sep 05, 2018 10:04 am Marty, it has about 150k on it currently. I would think a problem as major as you suggest would cause problems throughout the rpm band, not just at specific parts.
If the gear has not slipped much, the car is still drivable but won't act "normal". Here's a few signs of a slipped gear:

Hard starting
misfire
poor idle (if you can start it)
lack of RPM (no high end)
poor manifold pressure (vacuum)
Lack of HP development (gutless wonder)

I hope it's not a sheared key, as it's a lot of work to fix. A friend just went through this scenario, and after working on carbs, ignition, etc. figured out it was a sheared key.
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91blaze
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Re: Engine Troubles... Please Help

Post by 91blaze »

It is a bit hard to start hot but it fires right up cold, been assuming it's just the starter going out. I'll start with re-gapping the plugs and swapping out the jets. If that doesn't help then I guess I'll be digging a bit deeper. Hoping it's not a sheared key as I don't have the funds to be rebuilding the engine just yet. That was planned for the winter. It'll take a few days to get back out in the garage to mess with it but I'll keep the thread updated. Appreciate the help guys.

Also, as far as wiring goes, I have a relay and no resistor wire. Have full battery power going to the coil. Was using a Flamethrower but swapped in another brand just to rule it out.
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Re: Engine Troubles... Please Help

Post by terribleted »

Sorry Blaze missed your comment about retarding no help. I would do a compression test before I jumped back into the carbs. If you are going to re-gap the plugs that is the perfect time. Compression gives a very good indication of the engines overall condition. You may indeed be able to confirm or eliminate a cam slip issue with a compression test as well. If the cam has slipped some cylinders are likely to show a compression deficit due to valves not closing at the correct intervals.
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