Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Fuel Pressure

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von:
Update. This relates to the wet air horn to bowl gasket problem. I installed a Holley fuel pressure regulator and set it as low as I could get it, 3.5 psi per my gauge. After rebuilding and installing another carb ('73 Chevy carb), and spending hours on the air horn gasket surface, getting it to match up perfectly with the bowl. the gasket still gets wet. I tried a little experiment by putting the corner of a gasket in a pan of gas. It wicked like crazy, travelling vertically and soaking the gasket. My conclusion is that the wet gasket is caused by this wicking action and that they all do it. It's more noticeable on ones with gaskets that protrude in some areas.

Toronado:
Vacuum build up in tank from improper venting.
Dirt or debris in fuel tank can cause fuel pressure
going up and down, there either something
restricting the flow were pressure builds then releases
when blockage temporarily moves out of the way, or
the carb. itself is not set up right. eliminate one part at a time,
you purchased a new pump so not the pump, you say you tried a different carb. so not the carb,
BUT you have not redone fuel lines and cleared tank and replaced in-tank filter.
fuel pressure is not going to be effected by air horn gasket slightly leaking at the
levels your getting on your gauge. fix the blockage and install fuel pressure regulator.

von:
I verified it isn't a fuel pressure problem by installing a regulator and gauge with pressure set at 3.5 psi. It's not a tank or line problem since there's no fuel delivery problem at WOT and the tank vents are functioning properly. The wet gasket problem is also present on other Q jets I've observed or know about. I'm guessing it's a common occurrence that's not real noticeable so mostly ignored.

Toronado:
wet gasket means its not sealing because the air
horn and maybe the main body are warped,
with the warp certain channels dont work right.
Buy the thick gasket and if that doesnt works it must be sent to cliff
to be de-warped. Or second idea your power valve spring
is not the right one for your application and is closing
and opening sporadically.

von:
I disagree. I've had one unwarped by Cliff and also dressed the air horn on another myself so it fit the bowl perfectly. Thicker gasket made no difference. In fact I think it makes the wicking problem worse because of additional gasket volume. The power valve spring was not cycling. The test engine was a bone stock Chevy 350.

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