Intermittent Oil Pressure

dano said
Are the bearings the correct size? Did you measure the journals?

I plastiguaged mains and rods when I was building. They were on the loose end of tolerance, bit still in tolerance.

my68barracuda said
I did not see that you had checked the bypass at all, that is why I re-asked.
The issue you are reporting: intermittent low oil pressure goes hand in hand with an intermittent oil by pass sticking.
If it was excessive bearing clearances the oil pressure would be consistently low.
Anything is possible, but it seems that debris blocking a passage would also be consistent.
The oil pressure issue is intermittent, is that right? Sometimes it is fine, other times it is near zero at idle and maxes out at 30 or so at high rpm.
Or is it the oil pressure is fine when the engine is cold and goes to near zero at idle and maxes out at 30 or so when the engine is hot? Please clarify.

A sticky relief would be consistent with what I see. A big part of the reason I threw a new pump at it was just in case it was sticking.

It has low pressure hot or cold. I might get 5-10psi cold at idle, but my gauge only really starts at 5psi so it's hard to tell. Right after I rebuilt it, it was fine but a few drives later the oil pressure suddenly dropped to nothing. Shut it off, wait a few minutes, and it would be normal. One time with it just tickling the gauge at 5psi, I put the clutch in, revved it to 3000rpm and it just switched back to 60psi. The last time I drove it, it ran normal for a whole weekend, and then on the last day of my permit it just fell to nothing.

Since putting the new pump in, I haven't seen it go to "good". It has been reading low the whole time. It may just be to the point the bearings are toast, but I didn't see evidence of damage when I drained the oil last time. I've tried not to run it with the gauge at zero, but when oil pressure suddenly cuts out all of a sudden intermittently, I'm sure the damage is building up.