racecar

New LS6 race motor, new LS6 pump, LS2 pickup and pan, new O ring, the plastic plug is in back, the metal plug is in front, the oil pump spacer is on right. Had oil pressure problems on start up. Took the motor out, tightened main bearing clearances to .002, rods .0025. Put 2 new O rings on the pickup tube. Nice tight fit. Still had problems with weak pressure. ---Shimmed the pump bypass .145. Then the oil pressure came up slowly at 2000 rpm, went to 60 after 30 seconds, slowly went down to 32 (1 minute), then slowly (1 minute) back up to 60, then it is fine, shut down, restart, rev it up, fine 55-60 lb.
Let it sit overnight, same thing, at 2000 rpm slowly up to 60, 1 minute down to 30, 1 minute back to 60, then OK. It's like the oil pump is loosing it's prime on start up, or getting an air pocket in there Any ideas??