The Stovebolt Site Forums The Shop Area Engine Shop Rough Idle or stumble

I hope someone out there might have had the same rough idle or stumble issues I'm experiencing. It seems to run fine at higher rpms. I got my 6 volt 1953 3600 with stock 216ci about 1 1/2 years ago. Since then, I've adjusted valves, rebuilt carb. (rochester "C"), replaced wires, plugs, coil, points, condenser, cap, rotor, fuel filter and fuel pump. I have verified that the fuel tank is clean, and that there are no obstructions in fuel delivery. Air cleaner is new. Intake and exhaust gaskets are new and there appears there are no leaks. Vacuum hose to windshield wiper motor is good. Electrical system seems good. Compression measures pretty evenly (within 10-12%). I'm stumped. All I figure I can do now is a valve job. Anybody out there have any suggestions? Thank you.

Manny,
With a 216, can you run a rochester c? Mine is a b.
Is it stumbling on acceleration? If so, have you checked you vacuum advance for leaks and does it move when you accelerate. It should move.
Hope that is some help.
Mark

I just reread this. Your distributor should turn on acceleration. Sorry

It's really just idling rough or kinda stumbling at idle. Vacuum advance seems fine, yeah it moves. When I use the timing light, the ball (timing mark) on the flywheel jumps around in relation to the pointer. It's mostly hitting the mark, but moves a little forward and backward. The truck drives well and seems to be real strong when I cruise and when I hit the accelerator. It just idles rough at stop light and just sitting in the garage. If anybody has any ideas, I'd sure appreciate it. Thanks.

Have you tried adjusting the fuel mixture? You may be a little lean

I don't know if I would worry too much about it. One condition that can cause this is a worn throttle plate bushing in the carb. If you can wiggle it at all in it's bore then it is worn. I am talking about movement you would expect when the bushing holes become enlarged.

I think the timing wandering a bit is normal.

Check your point gap. Turn the engine & check it in 2 different places. You could have a bent or worn dist shaft. Check the shaft for excess side play. Pull out 1 or 2 spark plugs & see if they have carbon on the insulators. You might be running rich & carboning up the plugs. You might need a hotter plug. Try richening up the idle mixture like Sweet says.

If the ball is jumping around at the pointer, I too would suspect worn dizzy bushings. Will the carb react when you change the idle mixture? Make sure your idle circuit is clean in your carb.

Hey Manny--any progress?

Haven't made progress yet. Funny thing though, took it out yesterday for a drive and it's idling even rougher. Tried to adjust the idle to the rich side, no improvement. Tried adjusting to the lean side and it started to stall out. I did notice the tail pipe is black inside not gray like we'd prefer. Gonna try and get to it this weekend. I'll try and update very soon. Thanks.

Check your carb float adjustments.

What size main metering jet do you have? My 216 Rochester "B" has a .051 jet.
Hope this helps.
Mark

Dear bolt, I don't know which jet I have, but I will find out. I can tell you after much research, it appears I do have the correct carb for my '53 216ci. I was wondering, would the .051 jet you have be the same as the Rochester #51 metering jet replacement part? Thanks for your help.

Dear bolt, Do you happen to know what the high and low float settings are? It would sure help me. The Chevy shop manual shows what the low is, but it says to use a GM guage for the high, which I of course don't have. Thanks

All model B carbs float set at 1 9/32 with the air horn upside down from the gasket to the bottom of the float.

Thanks!!!