Start up after rebuild 2.7 engine

[jim fling]

I just got my decade old rebuilt engine started. I put oil pressure on the engine from a pressure tank before staring. Put in 10 quarts of Castrol GTX 10-30 oil and started it up. Oil pressure at the gauge 40 psi and fluctuating at first. Settled down to 40 psi at 2K rpm. Pressure dropped to 20 at 1K idle and stayed there. Temp up to 100 deg. and I shut it down. I am used to seeing 40 psi at idle and 50-60 at 1K rpm or higher.
Could either of the press. regulators be stuck? Also Dan Hall did the machine work in the engine and performed all the mods. including squirters. Dan did other older engines for me in the past and oil press was never a problem with those engines. I am worried that the scavenger pump is not moving the oil back into the tank fast enough. Press. regulator springs were at spec. during rebuild.
Help I'm frustrated and worried.
Jim

[Flieger]

The general rule is 10 psi per 1000rpm is acceptable. All the way up to 1 bar per 1000 rpm is fine. Usually it seems a bit non-linear for me. Idle is about 1 bar, 2000 rpm is a little over 20 psi, all these pressures are with oil about 180 degrees Fahrenheit.

Cold, the pressure spikes up to 100psi at only 2000rpm or less at which point the pressure regulator opens and pressure stays there until the engine warms.