The oil pressure guage in my 1980 is almost always pegged when the car is running, so I got an oil pressure tester to see if the guage was reading accurately. I hooked it up and started the car, and it read 80psi when cold, and came down to 70psi as the car got to operating temperature at idle. These numbers are a lot higher than it seems like they should be, and the guage in the car is apperantly reading fairly accurate. I have always assumed that the guage wasn't working so I never put much thought into it. Is it a huge issue to have oil pressure this high? Where do I even begin to look if there is an issue?

 

When mine started giving funky oil pressure readings a new sending unit took care of the problem...

 

Yes but he did say he put a mechanical tester on it.
And still pressure is high.
A couple things can cause high oil pressure.
Which oil pump is in your engine? High pressure/ High volume pump?
Main and rod bearing clearances?
And how heavy is your oil?

 

I guess I would rather have high pressure than low. But yours does sound a bit to high.
where to start.
Double check with a mechanical gauge, properly hooked up.
What oil are you running?
History of this engine? Someone change the oil pump? Stuck pressure relief spring in the oil pump?
Rod and main bearing clearance too tight?

 

ghost,

Seems to be some information missing here.
Did you just buy the car? Just rebuild the engine?

Here is my understanding of how the dash gauges work.
If the needle is zero, it's not getting any voltage.
If the needle is pegged, it is getting voltage but no resistance, such as OHM resistance.

Notice the water temp and oil press sensors in the block or head only have one wire.
The gauge already has 12V positive at the dash.
The gauge needs some resistance from a ground (NEG) to drop the gauge needle to something reasonable.
The resistance comes from a properly working sensor.

Next: The sensor must have an excellent GRD at the threads. Sometimes too much thread-sealant RTV or thread tape prevents a good GRD.

Question to you: Have you recently removed the sensor?
Where did you tap into for your test gauge? Under the distributor or near the oil filter?
Did you use a sealant?

I would not worry about 70 lbs. The valve covers gasket will not start leaking. The timing cover & oil pan gaskets don't care. Nor does the fuel pump gasket, china- wall or Intake gaskets. None are under pressure. Oil filter gasket can handle 70 + easily.

The only place that might show disapproval of HI O.P. would be the rear main seal. If it was installed correctly, it will hold.

And there is always the slight possibility a subpar oil filter is plugged up, bypass adaptor missing?

 

Yes, the mechanical guage showed 80 when cold and 70 when warm. I dont really know the history of the engine, this car sat in my dad's garage for 20+ years and he never really did anything with it. It is an L68 350 from 1971 that someone put in to replace the California 305. I guess my real question is should I be concerned about it enough to start digging into the oil pan and trying to diagnose what is going on? It's been running fine except for its using about 1 quart of oil per 500 miles, but there's no smoke coming out or anything.

 

Ok,

Maybe somebody at one time removed the oil pump and put a stronger pressure spring in place.
I would not worry.

You could put the front up on ramps and have a peek at the rear of the pan / rear main seal drips?

Likely hundreds of posters reading your 70 lbs and saying:
Must Be Nice !

 

Sounds good, thank you. I will move on to the other things that need fixed.

 

The weight of the motor oil being used can make a big difference. If you have 20w-50 or something equally as thick that could push the oil pressure up higher. Maybe some 10w-30 might make the engine happier in the cooler months.

The other option might be adding some Marvel Mystery Oil to you engine and see if it helps loosen up the pressure relief spring on the oil pump. It is also possible that the oil filter bypass is causing the issues so changing the oil to a lighter weight and put on a new oil filter should help.

Just don't forget the extra Zinc for the camshaft lobes when you change the oil. I use a bottle of Lucas Brand Zinc Additive in my engine every time I change the oil.

 

Don't worry about it.

 

When I put a new crate engine my oil gauge gets close to 80 psi when cold. I run 5W-30 synthetic since I have a roller cam.

 

The oil in it right now is valvoline vr1 10w30

 

The tester you used was a mechanical gauge that screwed into the same port as the normal electrical oil sender?

 

The engine could have been built with a high-pressure oil pump. If that's the case, no big deal. Or the oil pump pressure regulator could have failed...which is a big deal. If the in-car gauge seems to read similar to the mechanical gauge (reads 0 with engine off) and works as it has as long as you have had it, I would assume the issue is a high-pressure pump was installed sometime in the past. If you continue to use it "as is", just watch the in-car oil psi gauge OFTEN to make sure it is showing consistent pressures (higher on cold start, somewhat lower when hot).