Idle problems

[jwoodsmall]

When my '55 is at slow idle (500rpm) it is very smooth running (cold engine) but when I bring the rpm's up a bit it runs very rough. When on the road at a steady speed it again runs quite rough but when I accelerate it is very smooth. I dont know if I have carb. problems or electrical. I have installed new plugs, condensor, plug wires etc. and have checked for moisture in the distributor, but still have the above problem. I dont know what else to check????

[jwoodsmall]

I failed to mention that I also have installed a new carb and fuel pump as well as an in line fuel filter

[Joe Vandatta]

Could be tne vacuum advance since it's about the only thing left.
Joe

[nomadbird]

=====Wild Guess # 1======
As the engine speed is increasing, the breaker plate in the distributor will pivot. Is it possible that this movement is causing either the condenser lead or the coil lead to short out on the distributor body? How about the short ground wire from the plate to the distributor body; is it secure? As you can see, I'm starting with the cheap, easy stuff.

Tom D.

[ 08-24-2003: Message edited by: nomadbird ]

[sc1956]

Does it ping, start missing, act like it's starving? What's the nature of the poor running?

[jwoodsmall]

It doesnt ping at all, even when I get on it, but it does miss at a constant speed as well as at idle. I will check the wires etc.
Thanks for the reply!
Jim

[sc1956]

Wires and plugs would be my bet, followed by very poor valve lash on one or more cylinders. Have you tried pulling wires from the distributor one at a time to see which one doesn't affect a change?

[jwoodsmall]

I installed new plugs and wires, but I have not pulled each wire out of the dist. to see if I have a change. I will try that next!
Thanks
Jim

[sc1956]

If the plugs and wires are new, I'd definitely look to the valve settings. Did you take a vacuum reading?

[Joe Vandatta]

Try running a vacuum and compression test.
This will tell you a lot on whats going on.
Joe

[jwoodsmall]

I did a compression test and all of the cylinders come in at only 65-70#. Maybe this could be my problem. The only answer to the thing is probably one I dont want to hear!!!! Any oil (gas) additives that I might try, or do these things make things worse. I have added Marvel Mystery Oil to the gas for the valves as one fella told me this was what he uses in his old cars????
Jim

[sc1956]

Have you checked the valves yet? Low compression can easily be caused by horked up valve lash.

[Joe Vandatta]

Woody, if all the cylinders are that low (compression test) I think you are due for a major overhaul. There is no quick fix, don't waste your money
Joe

[jwoodsmall]

It sounds like I need to start saving $$$$ for an overhaul. I was hoping that it wouldnt come to that but Iam not surprized.
I appreciate all the advice from everybody.
Thanks.
Jim

[Joe Vandatta]

Jim,
One thing about it is if you get a reconditioned short block you can transfer all the stuff you've bought to it. Do you have any idea how many miles are on the engine you have, my bet is there are many.
Joe