I have an aftermarket electronic fuel pressure gauge in my 74.
It always reads 3-4lbs.
Shouldn't this number be higher when I rev the engine?

Reason I ask, I called Holley and they said my 700cfm dp requires a min of 6lbs of fuel pressure.

My gauge may be bad?

 

I'm guessing you are running a stock mechanical pump. Your pressure sounds about right. The cam driven lever pushes against a spring which moves the diaphragm whatever amount is necessary depending on how much fuel has flowed out of the pump so the max pressure is determined by that spring. I am sure that Holley would be positively delighted to sell you one of their pumps which can produce more pressure. As far as 6psi requirement that might be necessary if you were feeding 8 or 900 hp and needed that much pressure to force enough fuel thru the float valve. I am pretty sure 4 psi is enough to provide enough fuel to support what you're running. You might calibrate your gauge,there's a good chance it's a little off.
Ron

 

to many people build there motors for high hp when they really never use it put a fax hp sticker on it if you have more than 325 hp most people will never use it