[Spridgets] Oil Over Pressure

[Wm. Severin Thompson]

Regarding the excess oil pressure. I chased a problem with REALLY excessive
oil pressure on a race motor. On start up it blew out a solder joint in an
oil cooler. It blew out the rubber gasket on an oil filter.

The oil pressure relief valve goes horizontally in the block. The strength &
length of the spring, along with tolerances between the check valve piston,
seat, and the passage way the piston slides in. 

Upon achieving oil pressure, the relief valve allows oil to drain down to
the pan. At a certain point, oil pressure is equalized on either side of the
plunger, and a secondary hole allows oil to drain off from the back side of
the plunger.

In my case, someone had tried to drive out one of the brass plugs the
factory puts in the block, and a chunk had wedged out of sight in the drain
passageway. So, after the pressure tried to equalize and drain, oil had
nowhere to go, and it zoomed over 100psi.

In your case, pull the large nut holding the spring & plunger, and inspect.
Make sure you can feel the seat in the block. If all is right, either
shorten the spring, or purchase an adjustable pressure relief valve from one
of the usual suspects.