I own a 1971 Chevy Impala with a V8 400 6.6 liter, 2 bbl carb. The car sat for 10 years and I had success bringing it back to life It runs great until I drive it. It has a new carb, new coil, new plugs and plug wires. It seems to idle high in park until I press the gas, then the idle comes down. I can drive it for 20 minutes accelerating lightly. When I floor it sputters and shuts off. When it is warm it hesitates and then shuts off. I opened the hood to start it again and it shuts right off and I hear a sucking sound that seems to come from the intake manifold. I want to fix this without paying too much, can someone please give me some idea as to what might be going on.

I am new to the site so I hope I am posting in the right place as I don't believe this is specific to Impalas.

Thanks,
E

 

u have a vaccum leak somewhere, check all the vacum hoses for cracks, open ends etc, a sure fire way to find this out is to cover the carbuetor opening with your hands, it should stall, if not u have a vaccum leak

 

Yea, man I agree, Vacuum leak, all that old *** rubber there is a crack somewhere. Probably the hose from the intake to the vacuum block or brake booster. Plus I think your choke is open. On that car, I think there is a choke lever under the steering wheel. But if you put an new carb on there should be a thermal choke on it but I dont know what you put on.

Keep us apprised AND post pics, 71 Impala sounds hot.

 

Gents, thanks for the reply. I tried covering the carb and the engine did shut off. My carb is open and since it is an auto choke, I probably should have the carb adjusted. I'm thinking of replacing my entire intake and stepping up to a 4 barrel. I will get the pics up soon, although right now it isn't a pretty sight.

 

well before you do anything you have to get it running and keep it running. If you re sure you dont have a vacuum leak then I would suspect that your accelerator linkage to the butterfly is in the wrong position. Try adjusting that throttle linkage until you get the right idle without goosing the pedal. The butterfly should be wider when you start it up cold than it should be when its hots. And that is the job of the choke. Everything you describe sounds like your flooding the engine or offering too much fuel and not enough air. Choke issue again. If you have an automatic choke it could be electric or thermal. Check the coil element inside it if its thermal and make sure your wires are correct if its electric.

Also check the vacuum hose for the advance on the distributor. The timing could be off since it is an old fogey motor that was out of service for some time.