Originally Posted by 69chevyLWB
Fired up my rebuilt 388 chevy (350 bored .060 over and 3.75 crank) and it ran prefect but the oil pressure at 2500 was at 80 psi and would keep climbing the higher the rpms went. Got up to 4000 and she was close to 100lbs! we shut the motor down after this and had no leaks or other problems. Oil pump is in a package from summit which came with a 7 quart pan and a pickup. oil is straight 30w. no oil leaks or gaskets blowing out. just wondering if the relief spring isnt working or whats going on. bearing clearances are around .02-.03
Straight 30w oil is thicker when cold than multigrade motor oil (like 10 or 15w-30 or 40, like you'll presumably be using after it's broken in).
And the engine is spanking fresh. Likely once the cam's broken in and you are running the oil you'll normally be using, you'll see a reduction in the hot oil pressure.
If not, then
I'd be looking into the pump bypass spring being too stiff or piston sticking shut. Also be sure the gauge is accurate.