Why do I have high fuel pressure...

[patrickt]

Originally Posted by steve meltzer

Single Holley 4160/vac secondaries (Holley #0-3310C). Both mechanical pump and electric Holley.

I've owned the car for nearly 15 years and it's always run about 6 PSI at idle with either the mechanical or the mechanical + electric. On the road, same until about 3K RPM when, under load, the mechanical pump falters, dropping the pressure to 2-3 making the car stumble. Switching on the electric pump solves that problem and the pressure returns quickly to 6 and remains there, as long as the electric pump is on. Been that way forever, but now....

There have been a hundred million Holley 4160s with mechanical fuel pumps on the road over the last 50 years. None of them have ever suffered from fuel pressure starvation (mine included) unless: 1) The carb is way out of whack (floats set wrong, Moraine filters clogged and spring jammed up 2) the fuel lines are too small or clogged up; or 3) the fuel pump is broken.

I would first test the mechanical pump for both pressure and volume. The way you do this is right out of the service manual. Put a new pressure gauge, petcock, and tube in line right before the carb. Run the engine and, of course, you should have 4.5 to 6.5 psi. If it passes that test, then check the volume. Spec's call for it fill a pint jar in 20 seconds.