Reply to "Mechanical fuel pump recommendation needed"

Jeff,

that's the pump I referred to, I've not used it, it was recommended by a member of the Cleveland Forum a couple of years ago, I assume a recommendation infers he had no problems with his.

I calculated the fuel needs of a 350 bhp motor at 29 gph.

I thought I would use this opportunity to explain the advertised flow specs for mechanical fuel pumps. Mechanical fuel pumps do not pump at full speed constantly, their speed is dictated by the engine rpm. They also pump against a back pressure. The advertised flow figures are quoted for zero back pressure, at an unspecified engine rpm. They flow significantly less fuel with back pressure. The good pump manufacturers will normally provide a graph showing flow verses engine rpm for typically 4.5 psi back pressure. The proper way to specify the fuel flow of a mechanical fuel pump is to specify the back pressure and engine speed at which the quoted flow rating was achieved. For instance, the Holley pump is advertised as 80 gph, yet the real world flow is 38 gph at 4.5 psi back pressure and 6000 rpm. 38 gph will support 450 bhp.

I contacted the people at All Star Performance, they would not provide a fuel flow rating at 4.5 psi, or any kind of graph depicting fuel flow verses rpm, they only quote 120 gph, which is obviously a zero backpressure rating. However, using the Holley fuel pump's performance as an indicator (both are 2 valve pumps), even if the real world flow at 4.5 psi back pressure and 6000 rpm is only roughly 50% of the free flow rating, that is still 60 gph which will support 720 bhp.

Because I've read of several people having failures of their Holley fuel pumps, I perceive the All Star Performance pump as the best recommendation for a budget fuel pump, with a strong suggestion that the RobbMc Performance fuel pump be utilized if the budget allows. The smaller of the 2 RobbMc pumps, rated at 110 gph, actually flows 70 gph at 4.5 psi back pressure and 6000 rpm. 70 gph will support 840 bhp. That's a good pump!

Your friend on the DTBB, George