[bobcowan]

As said above, use a quality filter like Motorcraft or Purolator Pro-1.

There have been some basic design flaws with the Lima motor's oiling system. It was designed as a truck motor, and there are some problems in using it as a performance motor. BUT, Everything has been fine until recently, so clearly something changed. The trick is to find out what happened.

Fluctuating pressure like that usually means you're sucking air or the intake track is blocked. That's a bad thing. Don't run the engine for another minute like that. Pull off the pan, remove the pump and pick up. Clean it all up and see what you got.

It could be a clogged pick up screen, broken pick up pipe, etc. Don't put it back together until you find out what the problem was.