Just replaced a cracked piston in my 1969 olds cutlass 350. Starting it up to time it for the first time, I realized my 4 barrel quadrajet was overflowing a good amount of fuel ( about a cup every 1-3 minutes) out of what my service manual calls the internal vents. Also, engine runs good for about 10-15 secs, then almost dies, and repeats until it finally successfully dies. I believe this is related to the vents overflowing, and pouring excess fuel back into the carburetor, flooding the engine.
I have never worked on carbs, so any advice should be dumbed down please.

Thanks for the help in advance

 

Sounds like the float and/or needle valve is stuck. When fuel in the bowl evaporates after sitting a while, the float rests on the bottom and sometimes varnish 'glues' it there leaving the needle valve open to accept fuel even though the bowl is full resulting in fuel overflowing. Or sediment can obstruct the needle valve preventing it from shutting off fuel when the bowl is full. When fuel fills the bowl, the float should 'float' up, shutting off the needle valve and any more fuel from filling the bowl. This cannot be remedied without removing and disassembling the carb. Quadrajets are really easy to work with and rebuild even for a first timer. Take your time and follow the directions and it's a breeze. Good luck.

 

was not really sure what i was doing, but i did something right. I just took everything apart and then put it back together. now the flow has lessened a lot. still very occasional fuel being released from those vents, but nothing that would be even close to flooding the engine. I assume that a little fuel being released from the vents is normal. thank you so much for your help

 

There should not be any fuel from the vents I would replace the needle and seat as well as the float in the Q-jet

 

I agree, get a can or two of carb cleaner and get a carb kit for your car. It probably needs a good cleaning from sitting. If you need any help disassembling it, just post your questions.

 

Haven't driven since then, never actually got it running consistently succesfully. Carb is still flooding the engine, and it can not run for more than 10 seconds. When you say replace the needle and the seat, do you mean replacing the needles attached to the power piston and the valves that those needles go into?

Also, I have dissasembled and completely cleaned with a can of carb cleaner, replaced one of those needles because it was bent, and replaced all gaskets.

 

actually, a little googling and i figured out what they are. Let me check those out. Is there any way to tell if a needle or seat is bad?

 

Turns out there was no gasket for the seat, just put one on, now it runs well. Thanks for the help everyone, still got more problems though, check my other thread if you want to help.