fuel pump size

[Fired Up]

I'm selecting a fuel pump (mech) for my motor. Based on my carb (850), cu in. (454) and rpm range (6500) my motor math tells me I'll be flowing at least 726 cfm at 85% efficiency. Using these figures I will need a fuel pump that will need to flow about 45 gpm.
My question is this: If I get a fuel pump that flows 70 gpm, what happens to the extra volume of 25gpm (70-45) that the carb obviously doesn't need. Are fuel pumps built with relief valves? Or does the carb only take what it needs? Will the pump overpressurize causing leaks if the volume differential is too great? The lower pressure pumps I'm looking at (6-8psi) do not require regulators.

[shockwaveharry]

You need to run an overboard fitting of sufficient size (-12 min) to dump the excess fuel http://free.***boat.net/ubb/wink.gif . Just kidding. All it means is that the pump is capable of flowing a certain GPH at a certain pressure. if your engine uses more than 70 GPH, the pump will lose pressure. I'd go with the Holley 130 GPH pump and run a regulator. Cheap insurance since the price difference isn't outrageous and it gives you an excuse to build more power later.

[VitaminSea]

Also, upgrade the fuel lines from the tank to the pump to 1/2". Cliff

[propless]

What is better, mechanical or electric fuel pump?
Originally posted by VitaminSea:
Also, upgrade the fuel lines from the tank to the pump to 1/2". Cliff

[69 Elim]

I have ran both mech and elec pumps. nice thing about mech pumps is no wires to short out or come off in the middle of the lake. very reliable that way and more "fun time"