Oil level vs. Oil Pressure

[PeterHawk]

I have an early 289 engine (P88104) without the optional oil filter in my '62 GT Hawk with FOM. What is the relationship between the oil level as indicated on the dip stick and the oil pressure as indicated on the gauge on the dash? If the oil level is low, what should the gauge read?

[Mike Van Veghten]

Unless it's "really"...low...no change in pressure will occure.
As long as the pickup is getting 95+% oil vs. air, you shouldn't see any change.

Going around corners...when the oil moves to the opposite side of the pan and uncovers the pickup...then the pressure will drop toward zero very quickly...for as long as its even partially uncovered.

Old oil will drop pressure
Hot oil will drop pressure
A highly loaded, older engine will drop pressure (when loaded, like a steep hill)
Thinner oil will drop pressure
Partially plugged pickup screen will drop pressure
A pickup that's too close to the pan will drop pressure (if you've bounced the oil pan off a curb, rock or tire stop)
A stuck pressure piston "may" cause a pressure drop

Mike

[DEEPNHOCK]

To add to what Mike said....

Get your service manual out and read about servicing the pressure relief valve on the lower front RHS of the engine block.
(That's the pressure 'piston' Mike spoke of)..

That is a regular service item on a Stude V8 engine.
If it 'sticks', the engine oil pressure will vary with rpm and could be low, or high, depending on where the piston suck.

It's not hard to service... Just a total PITA (if the piston is stuck)
The good book has the procedure for you..
HTIH
Jeff

[PeterHawk]

When my engine is cold (first start in the morning) the pressure goes to 60, then settles to 40 and sometimes at idle at a stop light it might drop to 35. I guess as long as I'm holding at 40 I'll be OK.

[skyway]

"60 to 40 to 35" Many of us would love those numbers.

[maxpower1954]

Yes, all the Stude V-8s I've had run about 45-50 psi going down the road and around 10 at idle, fully warmed up. 35 at idle I've NEVER seen! Russ Farris

[KD0FRQ]

So should I be considered lucky to have 70-75psi at cold idle and about 50 at hot idle on my '64 289?

[rockne10]

If this is confirmed with an independent gauge, absolutely.
Realize, idiot lights on the dash usually won't come on until pressure has dropped to less than 5psi. If you are in running mode and that light come on you will be screwed in a very few seconds.
Average drivers would be happy with 40 cold idle and 10 hot.
I like oil pressure up to a point.
When we rebuilt my 289 I had the machinist polish each journal, then mic it and match a bearing to each journal. None of them were over 4/1000. At start-up the gauge is pegged. It about matches yours at hot and cold idle. I have been using Rotella 15-40 and am about to try 10-30 to reduce the oil pressure.

[Gunslinger]

Oil level is just that...how much oil is in the system. Oil pressure is essentially a measurement of the oil's flow. They're not the same thing, but insufficient oil level can affect the pressure as there's not enough oil to flow. The engine temperature, oil viscosity, cleanliness and a few other factors can affect oil pressure as well.

You don't have an "R" engine, but the oil pressure specs should be similar. In the Avanti owners manual, it states with an engine at normal operating temperature, should indicate from 45 to approximately 60 lbs. of pressure at 2000 rpm's. The oil pressure relief valve should open at 50 lbs. of pressure.