i was the one who didn't understand. i realized my mistake after re-reading your post.quote:
Originally posted by satterfi:
I don't know if most oil pumps have internal reliefs or not. I don't see how it matters if the relief valve is internal or external. They are set to control max system pressure, like 85psi. Maybe I don't understand your point.
however, given a clogged enough filter, the flow rate through the engine will indeed change. if the restriction is high enough to cause the pump to bypass, oil that would otherwise go through the engine is now just circulating through the pump.
an extreme, sure...
on the subject, it's amazing how much those pumps flow. i've seen 2 where the bypass stuck closed. one ballooned a 300psi burst rated racing filter enough to unseat the gasket. the other blew a regular oil filter like a tactical nuke went off inside. (it's amazing the oil pump driveshafts can live.)
also seen them with the bypass stuck wide open. in a ford 302 (the type of pump bob used, if i remember correctly), this caused idle pressure with hot oil to be ~2psi, and 2000rpm pressure about 20psi. actually, not bad, considering...
-michael