I have been reading a LOT about fuel pumps from the tech archives...
I purchased an OEM '87 GN gas tank and pickup ass'y. I have a 450-500FWHP carburated motor, and want to use a Walbro 307 pump. I am trying to build a nice reliable fuel sytem for my other car, and want to keep the pump in-tank. I don't want an external pump hanging down under the car, and also they are too loud.
From what I read, I know that since I only need 7psi, my fuel flow requirement is easier to meet since I am running closer to the pumps' "free flow" rating. I will be running the pump with less load since it only has to build 7psi at idle rather than 40psi, but at a higher pump motor RPM.
I also know I need about 35GPH fuel flow, plus a factor of safety, so let's call it 40GPH. According to the flow curves the 307 flows like 70GPH at my pressure! So...
1) Should I just get the Walbro 255 then? If the 255 flows 255 LPH = 67GPH free flow, that should be plenty at 7psi, right?
2) will there be any problems regulating down the higher pressure pump to run at 7psi?
3) Also how much louder than stock are the Walbros? They are still quieter than external pumps, right?
4) Last question... does Walbro have a web site? I cannot find a web site showing all of their product line.
With 500 hp and .55 BSFC (worst case), you'll need ~46 gph, call it 50 gph, just to be safe (plus you might find some extra hp later).
1) Either one will work, might want to go with which one has a better price.
2) You will certainly have to run an external regulator with a return line. I'm very sure that the pump's internal check valve will not be able to bypass the excess fuel during low fuel-demand conditions.
3) Not much louder than stock, I think they sound good. Much quieter than externals.
4) Dunno.
Ok then, .6 and 500 hp means 50 gph.