My all stock, all original slant six runs about 30-32 psi of oil pressure most of the time. Every once in a while i start it up and it'll run about 40 psi. Anyone got an idea why it does this? What kind of oil pressure is anyone elses engine running? I really don't know how many miles are on the engine but i'm guessing it's somewhere around 115,000.

your oil pressure should be a little higher when the oil is cold

Eric F took the words right out of my mouth !! I only wish i could afford an oil pressure gauge for my sweet slants !!!

Gauge should only cost about $10. If you want to keep the light, and have the gauge also, add about $3 for a "T" fitting.

_________________
Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Upgrading to copper line (over the plastic line usually supplied) is a good idea, too. Leave a nice loop in the system to allow for some flex.
I also painted the mounting bracket for my below-the-dash gauge. The red I used doesn't quite match the dash, but it's close enough for now.

Cold / thick oil will put more pressure on the gauge.

Most of my Slants run 30-35 psi at hot idle and 50-55 psi at anything over 2500 RPM or so, except for the HV pump I have in my wagon engine, that one runs 52 psi all the time, even at hot idle.

You may want to increase the relief valve spring pressure, that will increase the hight rpm running pressure. (external plug on the oil pump gets you to the spring, stretch or shim it up)
DD

The oil temperature doesn't seem to have anything to do with it. It usually starts up cold at 32 psi. The next time i start it and its warm it might be 42 psi. And it might be the other way around too. It just sporadically starts and has different oil pressures.

Maybe a flaky gauge?

A dirty or defective by-pass oil filter can also cause that.
DD