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Hi all, I'm having problems getting my car to idle correctly. My 31' has a 32' drive train and I'm at a wall in trying to get it to idle correctly. Basically I can't get it below 650 Rpm's, it has to have the idle mixture screw all the way closed, and it pub..pub...pub,pub...pub's out the exhaust pipe. I have the timing set at 15 degrees, plugs at 35, points at 20, and have a healthy dwell of 35. I've gone through all the wires with a timing light and none appear to be skipping a beat. It also has a rebuilt carb and I've checked the entire intake for any vacuum leaks. It revs up great and drives without any problems. It's just that it's idling to high and sounds like it's missing out the exhaust pipe. It's a little hard to start cold, but once it's warm it fires right up. At this point I'm just frustrated as I've tried about everything I can think of. The idle mixture screw has me puzzled as it really doesn't have any signs of a rich condition as there is no soot out the exhaust and the plugs are pretty clean. My next thought is that the float level is to high, but If you have any thoughts or suggestions I'm desperate for some help......

Did you check for a vacuum leak and did you do a compression test?

By the way, as a side note, the timing should be 18 degrees and the plugs should be gapped at .040".

Thanks Dog, yes I did check for vacuum leaks but couldn't detect any. I havn't done a compression test yet. It's worth a try though. I guess I ruled it out because it revs up great and I don't notice any blowby or fume issues typically associated with compression issues.

Do the compression test that way you have eliminated one more thing that could be causing your problem.

By the way, did you have the same issue before your carburetor was rebuilt? And, which carburetor do you have on your engine?

I'll have to look at the carb. number tonight. Prior to the rebuild (float crack and carb overflowed...found worn needle/seat) it didn't mis like it is but did require the mixture screw closed and needed a higher than normal idle.

I just remembered. I believe the carb is a 235S

The issue could still be the carburetor. You might want to try another carburetor as a test to see if that cures your problem.

If your car is a driver you can switch to a 569-S instead, which is a much better carburetor than the 1932 235-S.

When I had the spill over issue I was looking for a 569-S and couldn't find one. At this point I would consider switching if if meant better performance. Would you happen to know a source for a 569-S?

Your symptoms are consistent with improperly seated low speed jet. Could also be restriction in the idle circuit. Third check is the coordination of the metering rod and throttle plate. The 235S can run well if properly set up. I know that there are plenty that will tell you that they won't run well and to switch to a later model such as a 569S. I have run both and the 569S may be a bit better on fuel mileage as it is leaner.

Chipper, based on everything I've gone through it seems like it could be something like that. It's like there is something wrong in the idle circuit because once it revs past idle it's perfect.

The W-1 carburetors can be really tricky to get to run right. Once they are set up correctly they do a very good job.

I talked to the man that rebuilt the carb and he's recommending I get a vacuum reading off the manifold and do a compression test to make sure the idle circuit is getting the right signal. I plan to do that as it makes sense. He seems suspicious about the valves sealing. Can anyone tell me what the right range of psi per cylinder and idle based manifold vacuum should be?

Anything over 60 on the cyliners should be good. The vacuum from the manifold should be about 15 to 18....My cars are normally on the lower end about 16.

I checked our 31 over the winter and it checked 75,75,75,74,74,75.

Great.....

My manifold vacuum (taken from wiper port) was 16-17 at 650rpm's. It was bouncing a bit. Here are my compression findings.

1-80
2-80
3-70
4-75
5-70
6-80

Is it correct to think these readings are in the "normal" category?

I don't think you should have that big of range in compression readings. They should all be with in +/- 2 of each other. 10 is a little much.

The vaccum bouncing means a valves is not closing on a cylinder and you need to adjust your valves.

My gauge only has increments of 5. There might have been a little rounding involved. I think the 80's were more like 78 and the 70's more like 72. That said there was definitely a range of 5 or more.

......and I check the valves again over the weekend and have them set at 8 and 10 hot. While trying to getting things all worked out I decided to set them a little loose to avoid them being to tight.

Your readings should be within 10% from low to high.

You need to get that running....I'm waiting on my ride, and the weather is perfect for a ride!

Sounds like a valve grind is coming in the near future.

Gene, not really something I'll be excited to do but we'll see. At this point it runs good overall. A little uneven idle tone is about the only audible symptom. I'm still gonna tinker around in case I stumble across something. If I'm in need of a valve job as Gene points out is there a better test for that.....like a leak down test?

Wet compression and/or leak down test would be good to do after you have run the engine for a while. It can take a while for the internal engine parts to re-seat after a long period of inactivity. Once they have had a chance to "fix" themselves then the test will let you know more about what is needed. I have and engine that is slap wore out. Still runs, makes horrible noises when running but does the job well enough that I haven't decided to rebuild it yet.

A manifold vacuum gauge needs to be orficed (.010-.015) to obtain a steady value. If your gauge is not orficed, unsteady vacuum readings are normal. The vacuum signal in an inlet manifold is never steady due to the vacuum changes (pulses) caused by valves opening and closing.