Chevy 350 just quits running

Ok, I just purchased a 55 chevrolet with a 350 that has been installed in the car. It has a quadrajet carb and hei distributor. I replaced the plug wires and plugs. The engine starts immedietly and runs very strong both hot and cold. When the engine is cold I can put it in gear and don't have any problems. As soon as the engine gets to operating temperature around 190 it will idle fine for up to say 2 to 3 minutes then start acting like it wants to quit then go back to idle. It will do this sequence every 3 to 4 seconds about 5 times then just quit. If you put the car in gear while it is idling after it is warmed up like this even when idling correctly it will quit immediatly. If you can hold down the gas and work it a little to get it in gear without it quitting and keep the Rpms up to say around1,500 or better it runs like a champ and has no problems but as soon as it goes to idle even in gear it will quit again. I'm scratching my head at this point and need some advice.

"When the engine is cold I can put it in gear and don't have any problems."

Probably because the choke is on and the motor is getting the proper air/fuel mixture. Might also be a matter of the motor being sealed up when cold. I would suspect a vacuum leak.

If it was a vacuum leak why would it run perfectly at idle for 2 to 3 minutes then start acting like it want's to quit.

Could this be from a bad PCV Valve? Maybe while idling the pressure builds up in the engine? I'm just guessing. Thanks for the earlier response.

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Originally posted by jpblair55
If it was a vacuum leak why would it run perfectly at idle for 2 to 3 minutes then start acting like it want's to quit.

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That's why I said the motor could be sealed when cold, then warm up and warp the intake just enough to open a vacuum leak. I've seen it happen before. I'm doing this long distance and for free, so take it for what it's worth.

I had a problem similar to that a couple of times.

Once it turned out to be that the fuel pump push rod bore was damaged, and the push rod would bind up when the block got hot.

Another time, it turned out that the pickup coil in the HEI had lost its locator tit, and was rocking back and forth. This caused the insulation on the wires to crack, and would intermittently short out.

Another time, it was just the fuel filter in the Rochester carburetor.

Hey guy, techinspector thank you for your help and I'm not trying to be a donkey. I'm just trying to understand a fraction of what you do about engines. That's why I'm a rookie and you answer the questions. I'm taking all your advice Just trying to figure out the whole engine sealed up etc thing. I'll bother someone else, sorry. Firebird77clone thanks for your response also. I will be checking that tomorrow.

Quote:

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Originally posted by jpblair55
Hey guy, techinspector thank you for your help and I'm not trying to be a donkey. I'm just trying to understand a fraction of what you do about engines. That's why I'm a rookie and you answer the questions. I'm taking all your advice Just trying to figure out the whole engine sealed up etc thing. I'll bother someone else, sorry. Firebird77clone thanks for your response also. I will be checking that tomorrow.

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Don't get your shorts all knotted up, I didn't mean to imply that you were a donkey. All I'm saying is that it's difficult to troubleshoot someone's problem sometimes and I'm passing on what I perceive as good advice, although I am not correct 100% of the time.

I missed completely on one the other day. I was hung up on mechanical interference in the valvetrain when all the time it was an oiling issue which was correctly nailed by 76GMC1500.