I have a ZZ383 with a Mini Ram making 390 rwhp with 42 lb Bosch fuel injectors with the fuel pressure set at 40 lbs. I put the 255 lph Walbro fuel pump in after some a dyno session where the fuel pressure dropped back when I had 32 lb injectors set at 45 lb fuel pressure. With the bigger injectors at the lower fuel pressure of 40 lbs, can I go back to a stock fuel pump? Does anyone know how much horsepower the stock fuel pump can handle at 40 lbs fuel pressure? Reason I'm asking is when I'm driving at light throttle, like cruising on the freeway, for a while on very hot days, my fuel pump cavitates and I lose fuel pressure and stall. This doesn't happen when I'm on the racetrack running at full throttle. My theory is the high flow fuel pump is recirculating so much heated fuel at light throttle back into the tank, which returns right at the fuel pump, it is causing the pump to cavitate. I'm thinking a smaller stock pump would circulate less fuel and not cause pump to cavitate. Thanks for any input.

 

How about adding a second, lower voltage circuit that you switch to to reduce the flow when not needed? Assuming the extra flow is causing your problem, of course.

 

Thanks, that's a good idea. I might also redirect the return line to another part of the tank so it isn't dumping right into the fuel pump. I just found a 1LE tank so I can return the fuel outside the fuel pump sump.