big block oil cooler

[Guest]

I put a oil cooler on engine by makeing a adapter from where the oil filter bolts on and ran a large oil cooler and exteral oil filter try to run engine but couldn't get presure but as a test i disconected oil cooler and looped pipe round and engine got presure so i guess the oil pump doesn't flow enough to keep pressure with the extra pipeing ,since this happened I have tracked down a oil filter adapter off a diesel olds which has oil cooler pipes factory .This is not an easy task as I live in New Zealand .My Question is ,Are the oil pumps in the diesels high volume units so to have enough flow for oil cooler or will my one be good enough? also what is good oil pressure for an olds?