General Category > Quadrajet Carb Talk and Tips

Do i need a bigger needle and seat???

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Mr.Pontiac:
My bracket car was a consistant 12.20,s 107 mph car, decided to switch to a bigger hydraulic crower cam, Car now picked up et to 11.90,s but mph dropped to 102-3. do i need a bigger needle and seat, running a .135 now????

Cliff Ruggles:
What is the fuel delivery system?  What fuel pressure?

Mr.Pontiac:
Sumped tank, no.8 to electric pump and filter then no.8 to regulator and no.6 to carb.. Car has always ran 6.5 psi.

Mr.Pontiac:
New cam 296 HDP IF IT HELPS

Cliff Ruggles:
Difficult to say as you didn't put up the pump specs, type of electric pump or location.

Assuming it's at least 110GPH and located behind the tank the .135" seat should be adequate for the power level.

Never hurts to try a larger .140" or .145" seat to see if anything improves. 

My car is fine with either, didn't see any improvement going from a .135" to .145", but I left the .145" in place just to give me a "warm and fuzzy".

My system is also a sumped factory tank, 8an lines to a high flow filter, 140GPH electric pump behind the tank, and 8AN lines/fittings all the way to the nose of the carburetor.  Just ahead of the carb I have a pressure regulator set at 7.5 psi and return system back to the tank to take the load off the pump for "normal" driving......Cliff

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