What I have is a fresh rebuilt 401 with Edelbrock Pro-Flo EFI in an '87 GW. The cam is an Edelbrock #2132. The timing cover is the Bulltear nickle plated item. It has new oil pump gears and I am using the NAPA Gold #1258 filter. On cold start the oil pressure goes to 65psi right away. After the engine reaches normal operating temp (198 on the EFI controller display), the pressure gradually falls to ~40psi @ ~2600rpm and 60-65mph. When I let up on the throttle to make a turn off the hiway after an 11 mile hop, the pressure drops to ~15psi. When I apply some throttle the pressure comes back to ~20psi @ ~1100rpm and ~30psi @ ~1300rpm. If the engine is restarted after a half hour, the pressure @ idle will come up to ~20psi. If the engine is restarted after a few minutes, the guage does not respond until I add some throttle. Today, the outside air temp was 79-83 depending on which bank clock you looked at. Engine temps today: hiway 198 normal and up to 203, upon startup after a couple short stops before getting home 208 and 212. The radiator is a BJ's Offroad aluminum unit and there is 18 quarts of Prestone mixed 60/40 in the system. Oil is 10w-40 Valvoline with about 250 miles on the first change following the break in oil which was changed after a little more than an hour of run time. The guage is stock with a new sending unit. It was suggested by the engine's builder to tap in a mechanical oil pressure guage to verify the readings. I will probably do that but, I need some insight as to what is going on in this engine.
Thanks