My brain is shot from trying to figure out all the theories, so I'm throwing it to the masses
I've got a 468 BBC (about 500hp) with about 5-7 hrs on it. Last October and the last day of the season before I was going to bring the boat home I noticed my oil pressure dropping considerably when I was over 4K rpm's. Below 4K the oil pressure would peg itself back over to 70lbs, but as soon as I get above 4k it starts dropping and pretty quickly. The last run out I wanted to see if it would hold together so I let it eat When its cold the pressure stays all the way up (even above 4k rpm's) but as soon as it gets warm it starts dropping again. It dropped enough that I saw the oil psi bounce off 0 lbs It never made any noise and it was riding between 0-5lbs at about 5k rpm's long enough that it should've have been knockin loudly.
Since October I've been rebuilding the trailer and since thats done now I'm moving on to the motor. I dropped the pan and I can't find one hint of a piece of metal. The only thing I can find is pre-assembly lube. I ran a magnet through it and not so much as a hint of metal was found. I pulled both valve covers and there was plenty of oil up top including what I could see in the lifter valley.
Number 8 cylinder has a little bit of oil on the plug but nothing that would cause me to think I'm getting a ton of blow by. And I'm not losing any oil and it doesnt smoke at all. At WOT I can get a tiny amount of oil out the breather but again, nothing that would concern me.
I have a 10 qt. milodon pan with melling HV pump. Pan has windage tray and trap doors so I dont think the pump is having a hard time finding oil. I spoke to milodon about my pickup and they say I should have the high performance one instead of the one I have now. They said my current pickup is not that great over 4500 rpm's, but I can't seem to understand how my pickup would be the problem.
Recap: When its cold the oil pressure virtually never moves no matter what rpm. When its warm the oil pressure starts dropping above 4k but as soon as I let up a little the oil pressure jumps right back up. No metal found but my head hurts
Thanks in advance for the help!