I have an oil pressure problem with the 318 I just built, it has 15-20 psi max at 2000 rpm and falls near 0 at idle, it also has very little oil flowing to the rockers and the lifters won't pump up so it's not the gauge. The strange part is I can drive the pump with a drill at 1300rpm and get 50psi with plenty of oil to the rockers.

The oil pump is a M72 Melling, all the galley plugs are in place, it has clevite 77 bearings, full groove on the mains, standard rods, clearance it .0016" on the mains, .001" on the rods.

I don't think your pump spins that fast. There is a small press in oil galley plug near the oil pump that sometimes gets left out. Hopefully someone can remember where that plug is.

1300rpm on the drill(correct?) has 50 psi which is the same as 2600 eng rpm(give or take a bit depending if the cam gear/intermediate shaft in the valley area have the same # of teeth) but they're close enough in teeth count but at 2000 eng running rpm(only 600 rpm lower)it's 30-35psi lower. got too much clearance somewhere.

Is the plug in place next to the intermediate shaft?

plug in place ? rocker shaft holes sealing ?

Pull the distributor out and make sure the plug is installed in the left rear lifter rail. it is right in front of the distributor drive gear. I have had many come back from the machine shop with it missing. It will cause the same symptoms you have.

Found the problem, it was the plug in the rear of the dr side lifter galley, it has a 100psi cold and 80psi hot now, runs about 65 psi at idle.

I pulled the manifold to look for anything obvious while running the pump with the drill and oil was pouring out the rear of that bank onto the priming shaft, I threw a plug in the hole and it pegged the gauge running the pump with the drill.