Jumping Oil Pressure

[AMXguy]

Helping a buddy start his 383 and break it in this morning I found a problem I've never seen before. the oil pressure started out at 65 and after 15 minutes ended up at 40 hot, then it would jump to 50 or 60 like you flipped a switch and work it's way down again.

This is with a manual gauge, even put a new quality one on to see if it changed and it didn't.

It idles a steady 25 lbs hot, and never goes below 40.  any ideas? we've run it 3 times now for 20 minutes each and same results.

[Chryco Psycho]

bypass valve in the oil pump sticking or what lifters are you using? Solid or hyd cam ?

[AMXguy]

Hydraulic lifters, but they're quiet and the engine runs and sounds great.

[Chryco Psycho]

OK some of the solid lifters drop too low & open the lifter port which immediatly drops oil pressure is why I was asking .
 could have a cam brg problem too , was the cam tight to turn ?

[AMXguy]

No it turned real easy , I remember checking that close.

We drained the oil and it didn't show any obvious metal  even in bright sunlight but that's not too scientific.