Originally Posted by daveh
Thanks guys from all of the replys it sounds like I should go with the Melling standard volume pump below since the 340 isn't built over the top. All I know from the previous owner is that it's punched out 30 over with a purple cam and forged pistons. Looks like standard rockers nothing special.
Melling Oil Pumps M-72 - SummitRacing.com
high volume pumps are for low rpm protection, not high RPM.
Once the bypass opens the high volume will flow no more than a standard pump- BUT below it (lower RPM) you will have more flow and pressure. I like them for street cars especially ones that have shallow gears (low rpm most of the time).
High volume pumps work well at lower rpm, but at higher rpm the standard pump actually works better- where the crossover is depends on clearances, oil viscosity, temp, and your relief spring pressure.