General Category > Quadrajet Carb Talk and Tips

fuel pressure creep.

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dwelch:
this issue probably been covered about a million times but just seemed to pop up to me lately. i run a carter mech. pump (not sure which one) and a edlebrock 1904 q-jet on my 350 sb with cliff's kit in it. i have had this carb on a couple engines over the years without any problems. had some time on my hands so i hooked up a gauge just to verify everything was operating as it should. fuel pressure was about 5.5 when cruising and started to creep up to about 9.5 a idle. what seemed strange to me is that this combo runs great. it seems to be right on the money all the time. i know  the old saying "if it's not broke don't fix it" but i would feel better if everything was 5.5 all the time. hard to read plugs with all the additives in the fuel but they all look great with a light tan on them. don't know the age of the pump. this high pressure at idle does not seem to hurt performance. maybe it could be the good needle and seat and float in cliff's kits, just don't know. any thoughts?   Denny

Cliff Ruggles:
I've seen a few set-ups "creep" when "dead headed" or no return system used. 

Many years ago I purchased a Carter 120gph "high performance" mechanical pump.  For the most part it worked OK, but on occasion I'd get some minor flooding issues when hard on the brakes or sitting for a while at a stoplight.

I decided to do a pressure check, and it showed around 7-8 psi but would "creep" up to 12psi or even higher on occasion.  I ditched that pump, went to an electric pump with a regulator and full return system, and never looked back. 

All that happened in the later 1990's and the mechanical pump was marginal for the power level right to start with as I was also having issues with hard runs at the track running the bowl low.

That problem also disappeared with the fuel system improvements and I went on to sump the tank, move the electric pump behind the tank (Comp 140), and 8AN lines/fittings everyplace with a return system.

Best thing I ever did for my car and that system is still in place today and works flawlessly.  In all these years I've replaced the pump once and put brushes in it and on the shelf for a spare......Cliff

tayto:
Cliff, what about using a regulator like this one:
[url]https://www.summitracing.com/int/parts/sum-g3032/overview//url]

with a higher PSI mechanical pump?

Cliff Ruggles:
I use the same basic regulator from Holley, been dead solid reliable now for over 20 years....

dwelch:
thanks for the reply Cliff. ran that set up on my race only car for years. will start collecting the parts and be ready for the spring of 2019.  Denny

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