Very Low Oil Pressure in New Engine

The engine is a 71 318, RHS X-Heads, KB pistons, a Lunati cam, Hughes rockers, Melling HV oil pump, Kevoco Pan and pickup. The typical machine work was done and every clearance was checked when I assembled it. All the rods and mains were between .0015 and .002, but I don’t remember the side clearance or trust clearance off the top of my head and my notebook is MIA.

The oil pressure was about 60 PSI primed with an electric drill, and during the cam break-in it was almost 90 at 3K. Hot, the pressure was between 30 and 40 at idle.

After break-in (Lucas 30w break-in oil), the oil was changed (still Lucas 30) and I started to put some miles on it. I’ve laid into it a bit, but no full throttle and no crazy RPM. Everything has been peachy for about two weeks.

Two days ago I notice the oil pressure was low when idling at a red light (15 PSI), but came up as soon as I touched the throttle. The next day the pressure was even lower (between 5 and 10), still came up with RPM, but I stopped using the car. It had about 100 miles on it.

Today, I changed the oil to GTX 20w 50, but the idle pressure is still low and does not change with RPM. Priming it with the drill yields no more than 20 PSI. I removed the valve covers and no oil was making it to the rockers using the drill. I removed the rockers and nothing is coming out of the feedhole, though the gauge still makes it up to 20.

Since the engine is in an early A, pulling the pan is out. Before I do pull the engine to get to it I’m looking for something I may have missed. This is not my first engine, I’ve been playing with this stuff for 35 years but I am still stumped. Maybe I’m too close to see the obvious.

Any ideas?