Preasure relief valve

[unprr]

I'm trying to figure out why my oil presure goes up and down. At normal operating speed it shows about 60 % , I have the simple non-marked gauge. But when Icome to a stop or slow, the gauge goes very near to the low mark. I plan on running a slug clearner in the oil as well as taking out and testing the presure relief valve. First quetion, does the oil have to be drained and how do I test it.
P.S. I have changed the oil twice in the last 50 hours of run time, with high grade oil and filter.

[Eugene]

Sounds normal.

The pressure relief valve only works (opens up) at pressures of about 35 psi and higher. Below that, the valve is closed. A oil pressure below 35 psi, the pressure relief valve has no effect on oil pressure gauge reading.

Worn engine, rod and main bearing clearance, problem.

[lombard]

PRESSURE RELIEF VALVE IS STICKING OPEN----TAKE IT OUT AND CLEAN IT AND THE CYL. IT RIDES IN-----
CHECK RELIEF VALVE SPRING ( 9 LB. @ 2 9/16 " I THINK AT 83 I DONT REMEMBER THINGS TO WELL )----
YOU CAN CHECK IN ONE OF THE REPAIR BOOKS FOR THE LB. AND LENGTH------
IT IS EASY TO CHECK WITH A " U " BLOCK OF WOOD AND THE KITCHEN SCALE----
THIS HAPPENED TO ME WITH AN OLD TRACTOR----

[lombard]

DONT DRAIN THE OIL-------

[Matt Kirsch]

Oil pressure goes up and down with engine RPM, even on a fresh engine.

Get yourself a graduated oil pressure gauge, if you have a local Harbor Freight store they are cheap.

IIRC, 7PSI is adequate at idle.

I've tried using heavier oil, cleaning the regulator, replacing the regulator piston and spring... All wastes of time.

The bearings are probably a little loose, but if it's maintaining the minimum oil pressure and isn't knocking, you've still got time. Depending on how much you use it you might never need to do anything to the engine at all.