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.