Have a 302 in my brother's '69 Bronco. The oil pressure fluctuates with it quite a bit though.

Starts up where it should be but drops very low once it warms up. It raises when you rev it.

Unsure if it's nothing more than the temp of the oil causing it or something like the oil pump wearing out. Any way to determine the problem?

Thanks

 

Actually, that sounds normal. When it's cold, the oil pressure will be somewhat high due to the grade/viscosity of the oil you're using. When the engine gets to operating temperature, around 200 degrees F, the oil "thins" out a bit. Raising the RPMs increases oil pressure at operating temp because the oil pump is putting out more.

Ideally one wants to see ~10 psi oil pressure per 1000 RPMs.

 

Thanks, sounds about right.

Anyway of knowing of the oil pump is going out? Just ask because it's the original engine, don't know if it's ever been addressed or what to expect other than complete failure from it. I half expect the thing to be tired and maybe keeping things a little lower than they should be, but it could be a gauge error too, so I'm trying to fully grasp the problem.

Thanks

 

You're welcome.

If you have a mechanical oil pressure gauge, they're pretty close...as opposed to the factory "L H" gauge which is basically an electrical sending unit. The aftermarket gauges are calibrated to give you a number readout.....more reliable in my mind. There's no hard and fast rule for an oil pump going south other than really low oil pressure.....distributor problems....but that's usually indicative of other maladies.

But I'm sure you know all that.

An older engine with more wear and more berrin tolerances would show a lower oil psi with...say..a 10W30 grade than with a 15W40 or 15W50. Not too worrisome, or life threatening, just something to consider. The type/manufacturer of oil filters is a thought also.

 

If it helps anyone in the future, we changed out the headers on it and that's made a surprising difference. They had a few holes about 2 feet down (long tube) where they all connected. Oil pressure is up higher, engine runs a lot better too. Maybe they weren't seated right or something, seems odd to me that they had that much effect 2 feet down the line.