Originally Posted by ryan v
what's your guys opinions on high volume oil pumps? i've got a guy tryin to tell me they rob up to 30 hp and i should switch back to a regular oil pump. its in a small block chevy.
At 9000 RPM; like the water pump and the pump driven fan, the power extraction is geometrically variable by RPM. That is it goes up in exponents. At low RPMs hardly anything, by 6000 its getting up into the range of a couple, three horsepower, above 6 it goes crazy really fast.
That said there's different reasons for using a high output pump. If bearing clearances are exceptionally wide, if the engine is going to be used at high loading but low RPMs are situations where more than OEM oiling is warranted. The back side of this is oil control, if you're going to put more in the result is more windage. All this oil flying about the crankcase probably improves flat tappet life but it's difficult for the rings to keep out of the combustion chambers. This leads to the need for better control using strippers to catch the oil slung off the crank and direct it to the pan instead of allowing the crank windage to cause it to deflect up the right bank and into the cylinder bores. It's also a good idea to add a windage tray, but use one with a lot of vents facing into the direction of crank rotation to catch the fly-off and direct it into the pan. If this is a competition engine you also need added pan capacity simply to reduce the frequency a given thimble of oil gets cycled, a little rest allows time for entrained crankcase vapor to escape the oil. There is also a need for dams and doors that keep the oil around the pick up, this is a big issue with hammer head pans as these have plenty of space for oil to go where the pick up isn't.