Oil pressure issues

[jnormanh]

I recently bought a 1959 Lark VIII that a previous owner installed an oil pressure gauge in and that its readings concern me. When cold it indicates 20-25psi idling but quickly falls to about 5psi when warmed up, I should add that at no time has the oil light come on and it does work. Down the road at 55 warm is 20psi. I was told by the owner who is my neighbor and trustworthy that the engine was completely rebuilt about 10 years ago but has had little use in that time with less than 5k miles accumulated. My first thought was those pressures seemed low but perhaps it was a defective gauge, which I plan on replacing. But if those are the actual pressures my next thought was the oil pump. In doing some searching I find that only the oil pump gears are available and not a complete pump assembly. Does anyone know where I can buy a complete new pump? Also any other thoughts are appreciated, thank you.
Gerry

First off, before you do anything else, check the actual pressure with a known good gauge.

Secondly, people get far too excited about oil pressure. Engines require oil flow more than they require oil pressure. If oil is being supplied everywhere it needs to be, pressure, which is measured before the oil gets anywhere it needs to be, is almost meaningless. Maybe counter productive. You could have 50 psi at the gauge and 2 psi at the rod and main bearings. And, of course, the oil pressure at the cam lobes and valve stems is always zero. And that's not a problem. Back in the good old days, folks thought they needed to run 30 wt oil because it gave better gauge pressures than 20 wt. But remember, if you use thicker oil to get higher pressure out of the oil pump it always means lower flow where the oil is needed.

Nowadays we think 5W30 or 0W40 is better because it flows more oil to where it is needed when the oil is cold and thick.

When the Lotus V8 came out, the oil pressure gauge was marked L-N-H because the normal oil pressure for that engine was 5 psi hot and people would have panicked.

You could dump a few bottles of STP in it. The pressure at the gauge will come up, and the amount of oil delivered to the bearings and elsewhere will be less. IMO, those viscosity increasers, polyisobutylene, like STP and others did exactly the opposite of what was wanted. They increased pump pressures, and reduced oil flow downstream where it was needed.

Or you could run 5W30, lower pressure at the gauge, but more oil everywhere it's needed.

Those old GMC pushrod sixes ran 2-3 psi at hot idle, and lasted a long time.

With no symptoms of low pressure - like bearing knock, I wouldn't get very excited. Does it run well without any unexpected noises? If so, keep calm.

[kmul221]

Had a 55 Speedster once that ran 30-40 psi at speed & 5-10 at idle,I drove it for 5 yrs. like that & fellow I sold it to has been driving it for 10 yrs. like so with no issues.If I were you I would just drive it unless you want to spend a pile of $$$ to fix what doesn't need fixing !

[jackb]

once again, thoughts put forth (no one in particular) are a mix of old oil logic and days of daily driving.... who drives these 60+ year old cars 10K miles a year ? very, very, few. The low oil pressures mentioned for the Stude (or any other engine either) represent 1000-1500 driving miles a year. With 5 lbs @ idle and 25lbs down the road in an engine looking to 1000 miles a year, and newer oils.... who in their right mind would fool around building one excepting for a future sale ????

[jclary]

.... who in their right mind????....

Not to discount the value of your post...but the portion I chose to concentrate on, is probably the most often thought expressed toward any of us cherishing and clinging to our Studebaker(s)!

[gerry r]

Thank you all. The engine sounds fine both at idle cold or warm, and the same for going down the road. I am going to replace the gauge and sending unit and see what that shows.