Hi volume oil pump vs standard volume pump

Due to the 20% taller gears on the HV pump, the pressure will rise more quickly are the RPM's below where the relief valve opens. So at low RPM's and hot temps, an HV pump will maintain better pressure into the engine.

Just to clarify, when the pump's relief spring opens it does not return oil to the pan. It just allows some of the output oil to recirculate to the input side of the pump.

And, the torque and HP required to drive the pump only varies that same 20% when going from a standard pump to an HV pump. Any change in HP required is down in a fraction of an HP; the concept of 'power-robbing' with this is nonsense.

For Matt, IMHO it more depends on the temps and oil selection. In hot Texas, it might be better to have the extra hot temp pressure capability afforded by the HV pump. But if it is just a throw-together engine, then OK on the STD pump. Having good tight tolerances is more important.