Cliff's Quadrajet Parts and Rebuild Kits

Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: Jimpala on April 02, 2014, 03:10:24 PM

Title: Open or closed needle seat?
Post by: Jimpala on April 02, 2014, 03:10:24 PM

Is one preferred over the other?In Cliff's book he mentions the 70's Q-jets went to a closed seat for more fuel control. Jim

Title: Re: Open or closed needle seat?
Post by: Cliff Ruggles on April 16, 2014, 04:44:05 AM

The solid seats were introduced to help prevent drain-back during long periods of sitting.  No real performance advantage with either type......Cliff

Title: Re: Open or closed needle seat?
Post by: novadude on April 17, 2014, 06:21:17 AM

On this topic, is a 0.125 needle and seat enough for a 350hp small block.  I have a 0.135" seat now, but I think it is causing some intermittant fuel control issues with a Carter M6900 SBC pump.  Is a 0.135" seat really needed for every combo? 

Title: Re: Open or closed needle seat?
Post by: Cliff Ruggles on April 25, 2014, 04:15:43 AM

Any later carb will be fine with at least 7psi fuel pressure with the .135" seat.  Only the pre-1969 carburetors were fuel pressure sensitive.

I would not use a small seat for any engine making more than 250hp.......Cliff