After recent rebuild my 502 only gets 45-50# of oil pressure at wot. after it warms up it drops to 38-40#( at idle it drops to 25#). I've been staying under 4000rpms to be safe. I used all stock replacement parts the clearances are right in the middle of where they should be. All standard bearings, all plugs in place,I put a m77hv pump in, checked all my plumbing. It had good o/p( at least 60 psi) last year, the only diiference is i'm running 40 w oil instead of 20w50 and i'm running a 140* t-stat. I did drill a .030 hole to oil the t-chain.I've taken mechanical readings at all points and it's the same. Is there something i'm missing? This is driving me crazy. Please help i'm going crazy!

Sounds normal - see http://www.offshoreonly.com/forums/s...t=oil+pressure

I'm running two 502's in a 97 magic, and they put our 40 lbs. at wot, and 20 lbs. at idle. doesn't seem to change no matter what weight oil.

I think that GM builds their motors on the tighter side of clearances is the reason for the difference. I have the same issue with mine and my clearances are to the looser side of the range. Other than symptomatic low oil pressure after checking it twice during freshening no telltale signs of problems with 45-50 psi at WOT.

Doesn't sound that bad, but what are your oil temps? Did you install the cooler the correct way? Is the filter free of moisture, try changing it.
Gary

If you will look at this thread it will explain what local guy does to his blocks.
http://server2.boatfreaks.org/forums...&threadid=1193

Where are you measuring the pressure? Before the filter? after the filter?.. If you are measuring the pressure after the filter and you run a thicker oil... you may see a drop in the pressure if the filter doesn't have a built in bypass...... but the numbers you have posted are adequate for your engine.. I wouldn't worry.

Sounds ok to me had 1997 502 MPI it ran under 50 all the time. Had it 5 years had no trouble with it.