Oil pressure

[wuga]

I took my 31 RPU out for a nice run the other night. This block has 6.1 head, insert bearings and a down draft. When I started out my REX-A-CO gauge pegged at 6. By the time I got home, the needle was barely floating. I was running Brad Penn green oil. The next morning I did an oil change using 40 Pennsoil. When I started and drove the car, the pressure was again at 6. As the engine is run and gets warmer, should the pressure remain at 6 or drop slightly or even disappear? I want to do touring, but right now am afraid to move. Thoughts or opinions?
Thank you
Warren

[Will N]

Do you have a pressurized oil system with tubes feeding oil under pressure to the main bearings? This is the only way you should be concerned with oil pressure. If not, and you have the standard oil system and you just installed an oil pressure gauge to monitor things, do yourself a favor and rip it out. There may be some pressure in the oil gallery that leads from the pump to the valve chamber, but the gallery is wide open and meant to feed an overflow of oil volume to the chamber. An unrestricted gallery will register near zero pressure, particularly as the oil warms and thins.

[J Franklin]

Your gauge tells you the pump is turning. There is not much pressure when things get hot, Just volume. If you are really concerned drop the pan or remove the oil line and see how things are working.

[wuga]

I purchased this car last year and understand very little about the engine oiling system. The engine was rebuilt by Bert's in Denver CO in 2014 and was only started occasionally but never driven until last summer. Bert's invoice states counterbalanced crank, new main and rod insert bearings and high compression head. It goes on to mention new oil pump drive gear and rebuilt oil pump. I don't think I have a pressurized system. The car came with the gauge as well as a temp gauge. I have installed a Vintage Precision thermostat housing and still run the original two blade fan. Temperature is always normal.
Thank you
Warren

[WHN]

Originally Posted by J Franklin

Your gauge tells you the pump is turning. There is not much pressure when things get hot, Just volume. If you are really concerned drop the pan or remove the oil line and see how things are working.

This is my view also.

Cold engine, has more pressure showing on gauge. Heavier weight oil, more pressure showing on gauge. Long summer drive, less pressure showing on gauge.

It’s all about the oil flow.

Enjoy.

[Big hammer]

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I would suggest checking the 2 blade fan, if it’s a stamped steel fan change it too a aluminum two blade fan ! Check with a magnet

[Rob Doe]

This question has come up at a local club meeting a couple times, so it is not uncommon. Here is my take on it. It is a bit redundant but includes an analogy.

When i first viewed the internal workings of the Model A oil pump, I realized that it is essentially a pair of gears being driven off the engine that are moving the oil. The Model A pump is like the pump in the rear case of a general aviation piston aircraft engine. My own aircraft will pump 100+ on initial startup on a cold morning. The gears in that pump are smaller than the Model A gears, but may be turning at a faster speed.

Liken the low pressure seen on the Model A gauge to a garden hose, where the spray nozzle has been removed from the output end and the faucet turned wide open. The only restriction would be the friction drag of the fluid / water flowing through the hose. When the spray nozzle is reattached and set for a jet stream, the line pressure rises, shooting the small diameter stream several feet under pressure.

If the Model A pump were pumping oil through a labyrinth of passages to main and rod bearings, overhead valves etc. with only .0015 thousandths openings at the far end, it would show normal engine readings of ?? pounds.

As a young man, I had a friend who was a Model A engine builder that specialized in winning engines for Model A hill climb events. He was pressurizing the mains and adding hidden nitrous oxide bottles to the stock Model A engines! There are some old time racers on this forum and I seem to remember some quoting readings ... 25 50 and up.

[nkaminar]

The insert engine with pressure feed that came with my car read 50 psi with an aftermarket oil pump. I changed the spring for the pressure relief valve when I put the pump in my Burtz engine and now it reads 25 psi. It does not change much with temperature because the oil pressure is controlled by the relief valve.

[Ernie Vitucci]

Good afternoon...It sounds to me like you have a stock oiling system which would record almost no preasure with the engine at operating temperature. You state that your engine does not overheat...so it is beging cooled by oil and coolent as it should be. I would suggest that you call Burts and see if they have a record of the rebuild by the engine number. They're good people and I'll bet they have the records. Since you have the invoice, you know what they recorded on it. In speaking to them they will then confirm how the engine left their shop after a normal rebbuild. Ernie in Arizona

[Dean Lemoine]

Why not call Bert’s and ask Steve about the engine? I have an engine from them with all of the neat stuff you mentioned. Pretty sure you have a stock oil system.

[1crosscut]

In addition to reaching out to Bert's you can loosen the fitting on the right side of the block where the oil pressure line attaches. If you have oil seep out past the threads its working. Be sure to have someone at the key to turn off the engine in case the fitting accidentally comes all the way out. It will push a lot of oil out in a short time if it does.
I'm dang near positive you have nothing to worry about. The stock oil pumps are pretty much bullet proof.

[Synchro909]

As has been said above, it sounds like your oiling system is standard and as Mr Crosscut says, if that is so, you have nothing to worry about.
The engine in one of my cars has a standard oiling system and I love showing people the gauge reading zero when the engine is hot and idling. The looks on their faces when I keep turning up in that car make both my wife and I smile. They think we are just happy to see them!

[CWPASADENA]

Your engine is just fine,

Run it!!!

Chris W.

[wuga]

Thank you everyone for your input. You have put my mind at ease. I have been playing with cars for 60 years but never had a banger. This is the most fun and the best learning experience i have ever had.
Thanks again
Warren

[jack backer]

Banger? Dont say that here, they will think you’re a hotrodder😀

[Randall]

this might help you understand how the oil system works https://youtu.be/9YXjaxxC7rE