Fuel Pressure question

P

PC/SR

Well-known member
I am running dual Holley 94s (on a Model A 4 banger) which call for 3 psi fuel pressure. Have a Napa 4-7 psi elec fuel pump, and a Holley 804 1-4 psi regulator. Factory adjusted to 2.8 psi. On a cold start it measures 2.8-3 psi. Question is, as the car warms up, at idle or otherwise, the fuel pressure slowly drops to around 1 psi.
Originally had a Napa 1-4 psi pump without a regulator, and at the pressure gauage near the carbs it was 3 psi. Same thing, as it warmed up, psi slowly decreased, to zero with this lower psi pump.

I know pressure will drop some as the float valves open. But it does this at idle, when there should not be a problem keeping up with fuel usage, and also when running. Any ideas?
PS--Did change pressure gauges and readings the same. Thanks
 
I was always under the impression that so long as the pressure did not over power the float and cause over filling/flooding of the float chamber the pressure could be even 1/2 psi so long as the volume provided enough fuel to keep the chamber at proper level.
 
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What gauge are you using? The liquid filled ones will read less pressure when they get hot as they are not vented and as the liquid heats up it acts against the pressure in the gauge internals.
 
There have been several threads on the HAMB on having to drill a hole in the gauge to get it to work correctly. Don't remember the size or location.
 
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