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Author Topic: Open or closed needle seat?  (Read 2051 times)

Offline Jimpala

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Open or closed needle seat?
« 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
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Offline Cliff Ruggles

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Re: Open or closed needle seat?
« Reply #1 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
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Offline novadude

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Re: Open or closed needle seat?
« Reply #2 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? 
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Offline Cliff Ruggles

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Re: Open or closed needle seat?
« Reply #3 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
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