Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Open or closed needle seat?

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Jimpala:
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

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

novadude:
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? 

Cliff Ruggles:
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

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