Thats kind of an open ended question. The answer would really depend on the amount of milage and service life of an engine. My old 350 (removed from my great grandfathers '77 caprice classic) with about 175,000 miles, when warmed up, would hold about 33 psi while driving and 15-20 psi at idle. My new 350, when warmed up, will hold at about 55-60 psi while driving and about 35-40 psi at idle. When it is first started up and cold, engine oil pressure usually goes about 85+ psi. I believe that the general rule of thumb is a minimum of 10 psi @ idle and another 7 psi for each 1000 rpms.
1973 K20 - 350/465(as of 10-04-03)/205
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