272 Y-block, low idle miss/lumping?

Tom in TN

Tom in TN

Senior Member
Freshly rebuilt 272 (now app. a 281), stock 2bbl carb, stock cam and factory adjustments - has been running fine for about 1500 miles.

Last weekend, all of a sudden, it started runnning really rough when at idle - almost like 2 of the cylinders have cut out. I've pulled the plugs and they all look good.

Once you give it some gas and raise the rpm, it smooths out and runs just fine.

Any suggestions from the wealth of knowledge in here?

Motor in question:
newmotor-09p4.jpg


TIA
 
My 56 did the same thing. It sounded like it had a hot cam in it. I found the problem and the dist. was the problem. The bushings were shot and I got a rebuilt dist. at NAPA and that solve the problem.Take a smal magnet and run inside the dist. to see if any metal shavings.Check shaft in dist to make sure it tight and no wobble.:D
 
That would be my guess also dist.If you remove dist and see if loose,when out, turn up side down clean the dirt and oil shaft.It may make it worst.
 
ken ct said:
Set idle mixture screws the 2 with the springs on them to 1 turn out from closed.ken ct.
Click to expand...


Ken, Starting adjustment was 1-1/2 turns out.

I set them to 1 turn out and the motor wouldn't idle - kept going dead.

Then set them to 1-1/4 turns out and it idles and is a little smoother than before.
 
For those that responded...(do threads jump back to the top? if I reply?).. anyway... I found out what my problem was... the carb.
We went on a run Sat and it stopped being able to idle.
I pulled the carb and stuck on one that I had bought from Ken ct a few years ago, that had a bad accel pump in it...and it idled just fine..just would bog down when giving it any gas.
So, I took the accel pump out of the bad carb and stuck it in my 'ken rebuild' and now she runs just like a top.
I suppose there must be some trash inside it...OR the Ethanol has gotten to something in the idle passages.

Thanks to all that replied!
 
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