Hey guys

I rebuilt my Rochester Quadrajet 4bbl for my 307cui olds engine. I also changed the needle seat. Originally I had the closed needle seat (left on picture) and now I have the needle seat like in the middle of the picture.
Now I have the problem that the engine dies on idle. First it runs normally and then time to time the idle drop until the engine dies. Could that be the new needle seat?
At all what are the differences between the needle seats? And which seat for which adjustement?



-98regency-

 

Their are two difference in seats. One being the diameter of the hole in them which dictates how much fuel can pass under maximum demand. It also plays a minor role in setting float height but not enough for most to ever notice.
The second difference is the milled windows or holes drilled in the seat which let the fuel come out the bottom of the seat instead of taking the long restrictive route past the needle body and spraying into the carb top. The help control the fuel better and it doesn't get aireated as with the solid sided seat.
After you changed the seat did you also reset the float height. If not that may very well be your problem. If the float is low the carb may not be able to consistently draw fuel up the tubes. If the float is high you could be flooding it.

 

Thanks for your answer! I didn't adjust the float level after I changed the needle seat. I don't know how much.
So I changed the needle seat back to the originally "closed" seat and now the engine runs normally in idle and doesn't die anymore Thanks!