Oil pressure issue

[scottyz]

In my 80 I have a 383 small block. The oil pump is a m55HV with a stock oil pan. No windage tray. Oil filter bypass has been plugged. When the vehicle is hot at idle my oil pressure is about 25-30 psi. At a steady cruise at say 2000, 2500, 3000, 3500 rpms the oil pressure is about 65 psi. If i get on it and stay in it to rpms in excess of about 4700 the pressure will steadily start to drop. I usually let off when it hits about 25-30 psi. Lately i have been noticing that if I leave from a dead stop with moderate throttle the vehicle will shift to second and then the pressure starts dropping off again towards 25 psi then will start to climb again. If I let off the gas completely the pressure rises right back up to 65 or so. I havent brought the car to the track cause of this issue. Any ideas?

[TPI Monte SS]

At a steady cruise, the oil is circulating quick enough, but it sounds like the high-volume pump is either sucking the oil pan dry under WOT, thus losing pressure. Another possibility is the oil is being pulled away from the pickup tube on a long WOT run, and causing low oil pressure at high RPM. I'd guess you need either a larger pan with a better baffle, or a regular M55 pump.

[DRCE]

Seen this plenty of times. Oil is creping up the back side of the back under acceleration and away from the pick-up. This is typically seen when a windage tray isn't used or with high volume pumps and oem displacement pans.

I would loook into a rear main cap baffle. It is a cut to fit type of unit but it will stop the oil from climbing the pan.

[chicane67]

It could also be, and most likely is, a drain back issue.

If it were just the oil climbing up the back of the block, the pressure would wildly change from the pick up being uncovered. But it is most likely a combination of both........