Engine: Oil pressure issues

[gerry r]

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

[jclary]

There are knowledgeable folks here with much more credibility and experience than I. So, be patient, and perhaps some will add information helpful. In the mean time, I'll ad a few comments. "Rebuilt," unless you witnessed it, is always a suspect term. To some, replace bearings, and/or rings, is considered rebuilt. How much honing, oversize, undersize, valves, stems, rockers, cam bearings, line boring, etc. etc., and so on...?

Is there an oil filter with a missing flow restrictor fitting? And as always, (I've never been so lucky), is there an incorrect oil gauge. In the case of the cars with the simple oil (idiot) light, I've heard of them giving you an OK indication with less than ten PSI of oil pressure. Honestly, I think the Studebaker engines are sturdy enough to allow a lower oil pressure than many makes, as long as there's sufficient oil "flow." Of course, PSI & FLOW are related, and I don't know the mathematical specs.

You have not mentioned (unless I failed to comprehend) oil pressures on the road, underway. I have had engines that had fair oil pressure, at speed, and showing little when idling, that ran great for years. On our Studebaker engines, there's the ever present, often overlooked, oil pressure relief valve. If neglected, it can suffer from restricted movement, and affect pressure reading.

Do the easy things first, to verify the readings. Install a good gauge to verify pressure, and service the oil relief valve. Do not stretch the spring. If need be, replace it. If it is truly low oil pressure, and the flow is too low, unless I'm wrong, oil through the engine returns over (and lubricates) the timing gears. Too little flow there, and it can cause premature failure of the fiber cam gear.

As for oil pumps, unless the engine has really been neglected, a lot of grit, metal debris, or hard carbon deposits pumped through it, not likely to be worn. After all, it is constantly bathed in oil. A good place to check is the front main & rod bearings. Being softer metal, those components getting the first crack of pressurized oil, will have small particles of harder materiel embedded in them. Hope this helps, & wait for others to either verify or endorse my (suspect) comments.

[sailingadventure]

And there`s always the possibility that the last guy left out the oil gallery plug below the distributor.

[gerry r]

I may not have made it clear but in my original post I put at 55 with the engine fully warm it pumps right at 20psi indicated on the gauge. Thank you to both for answering and any more suggestions are welcome and appreciated. I have a local Studebaker owner that seems to be quite knowledgeable looking at it and he told me that he has already replaced the oil pressure relief spring with no change and he tells me that in his opinion wear does occur to the inside of the oil pump casing over time that just replacing the gears does not address hence his suggestion too look for a entirely new pump.
Gerry

[rusty nut garage]

The oil pump is the first thing to get oil and the last thing to run out. Oil pump wear isn't normally an issue on the stude v8. Camshaft bearing wear, rod, and main bearing wear are typically the problem with low oil pressure. Also excessive wear on the rocker arm assemblies will also add to the low oil pressure woes. The missing oil galley plug in the distributor tower area is a common mistake, not sure what the oil pressure would be without that plug, low to none I'm assuming.
Studebaker engines can survive on low oil pressure and while it makes me a bit concerned at these levels the motor will survive for quite some time with these pressures. Here is the approach I would take.
1. install a good known mechanical gauge and check confirm pressure.
2. remove distributor and inspect for missing oil galley plug
3. if partial flow filter block then temporarily plug pressure port at block. If oil pressure increases inspect oil filter assembly for restrictor fitting.
4.run 50 weight racing oil
5. IF still concerned at this point, IMHO you'll need a quality rebuild.

I may not have made it clear but in my original post I put at 55 with the engine fully warm it pumps right at 20psi indicated on the gauge. Thank you to both for answering and any more suggestions are welcome and appreciated. I have a local Studebaker owner that seems to be quite knowledgeable looking at it and he told me that he has already replaced the oil pressure relief spring with no change and he tells me that in his opinion wear does occur to the inside of the oil pump casing over time that just replacing the gears does not address hence his suggestion too look for a entirely new pump.
Gerry

[GrumpyOne]

Malfunctioning pressure relief valve spring?

[64V-K7]

Change the oil to a good grade 20-40w (Valvoline?) or even a straight 30w and check it out again.

[rockne10]

And there`s always the possibility that the last guy left out the oil gallery plug below the distributor.

It's my understanding that, under any idle situation, this would result in a reading of zero pressure.

[rockne10]

... wear does occur to the inside of the oil pump casing over time that just replacing the gears does not address hence his suggestion too look for a entirely new pump.

I've also found, at least in the six cylinder, simply honing the oil pump cover plate will significantly improve the pressure.

[wdills]

When my engine was rebuilt with the plug left out, it would start cold and idle at about 20 psi and fall below 5 psi when it came up to full temp. Mine never dropped all the way to 0.

[PackardV8]

The oil pump is the first thing to get oil and the last thing to run out. Oil pump wear isn't normally an issue on the stude v8. Camshaft bearing wear, rod, and main bearing wear are typically the problem with low oil pressure. Also excessive wear on the rocker arm assemblies will also add to the low oil pressure woes.

"Rebuilt," unless you witnessed it, is always a suspect term. To some, replace bearings, and/or rings, is considered rebuilt. How much honing, oversize, undersize, valves, stems, rockers, cam bearings, line boring, etc. etc., and so on...?

The above is for true. When I'm asked about a rebuild, I know CASOs will always comparision-shop and I give them a list of operations and parts to make sure they're comparing apples.

simply honing the oil pump cover plate will significantly improve the pressure.

Again, for true. New gears and shafts, with the end play properly set, usually are worth the money.

jack vines

[Lynn]

Before checking out anything else, I would screw in a good temporary mechanical oil pressure gauge. You MAY not even have an issue.

If it confirms the low oil pressure, then pursue the items set out above, starting with the easiest and least expensive. It will cost you nothing to pull the distributor and confirm the presence of the plug as set out in post number 3.

[gerry r]

Change the oil to a good grade 20-40w (Valvoline?) or even a straight 30w and check it out again.

These readings were done after I changed to Delo straight 30

[doofus]

End play properly set sometimes means using a surface plate to "Shave" the oil pump body a few thousandths to get clearances right,effort well spent. Luck Doofus

[Mike Van Veghten]

Gerry -

The Stude V-8 tends to run a little lower pressure thAn most engines.
As has been said, you can "blueprint" the oil pump to gain some pressure.
Another loss location is the various bearings, including the cam bearings. Excessive connecting rod side clearance will drop pressure from the system also.

So yea, there's a LOT of locations to look. If the engine rebuild wasn't done with a careful hand...!?
A way of upping the pressure, but be aware...it does NOT "fix" the low pressure problem, is to use thicker oil. It just has a harder time going thru the system, but again, does not fix, just disguises the basic problem.

Also a fact to think about. This isn't so much apples to oranges as you might think, but many (non-supercharged) drag racers run a very low engine oil pressure (and a minimum trans. pressure). Why, releases more power to the driveshaft. Pumps take power to drive them. I have a friend that runs a small inch, big block Chrysler in a dragster that runs only 50psi at...10,500 rpm at the finish line at over 173 mph.

Mike