Engine: Low 289 Oil Pressure om '62 Hawk

[chet445]

My 289 engine, in theory, had 6K miles on it after a rebuild when I purchased the car. It starts out with 40 lbs and after it warms up pressure drops to 10 lbs and stays there regardless of the speed. I thought maybe a new pressure relief valve from SDI might help but no change. I welcome any thoughts. thanks, Chet445

[Bud]

Generally loose bearing clearances will cause low oil pressure, but there could be excessive wear in the oil pump causing the low pressure. The engine in my 62 GT develops around 70 psi when cold and drops to 55 at cruise and around 25 at idle when the engine is warm. It's possible that there is an internal leak in the engine around one of the internal plugs, but I don't think that is likely as the pressure is at 40 psi when cold. As an added note what grade oil are you using as a lighter oil such as 5W-30 may be too thin ? Bud

[skyway]

"Generally loose bearing clearances will cause low oil pressure"

...and not just the mains & rods; worn cam bearings can also be the culprit!

[PackardV8]

From back in the day, we do a test which requires pulling the rocker covers, intake manifold, valley cover and oil pan. A one-gallon container is filled with motor oil and a hose connects it to the oil pressure line to the oil filter. The container is pressurized to 75 PSI and the valve is opened to feed the pressurized oil to the engine. A full size drip pan is needed underneath, but very soon it becomes obvious where the oil pressure is being lost. Seeing the cam bearings is the most difficult and determining if it's coming from there or the crankshaft.

jack vines

[chet445]

I may well need to pull the engine and see what was done regarding the rebuild I was told occurred when I bought the car. I am using 10-40 motor oil. Thanks for the input.

[swvalcon]

Chet may as well pull it and start over. A lot of people call a rebuild if they pulled it apart cleaned everything and just put in new rings, bearing and gaskets but never checked to see just how worn out everything was.

[Bud]

It is very likely that someone did a back yard rebuild without removing the engine from the car. I'm betting that the engine has standard bores with original pistons, a standard crankshaft, the cam bearings were not replaced and the crankshaft journals were not reconditioned leading to excess bearing to journal clearance and low oil pressure. Someone may have replaced the rings and bearings and did a parts store valve job, then called the engine rebuilt. Most Studebaker engines at this stage in their lives need to be bored oversize, cam bearings replaced and the crankshaft needs to be turned the correct undersize to get all of the clearances within spec and to get the piston rings to seal correctly. Bud

[doofus]

First things first, are you using a known good gauge if so Jack Vines has a welcome test that still works but is usually ignored. Most shops, including Dealerships will just yank the motor for the hi-buck rebuild that might not be needed. havent seen a Bearing Leak Detector since Votech school. Luck Doofus

[jackb]

I once had a 289 from a 64' Hawk in my 62' Champ that upon the oil pressure light coming on, I found the camshaft bearings in the pan. Engine ran fine without noises, tho it got hot (I personally put 90+K miles on the engine). With a good, German pressure gage, I had 5lbs @ idle. I've heard suggestions that 5lbs at 500 rpm's is fine in an old engine. I'm suggesting maybe not. To boot, I also had 1 cylinder head cracked, and exhaust valve seats nearly destroyed.....I should mention that this truck hauled firewood, engines and made many a 500 mile trip.....and with a good working AC unit....full inspection suggested...

[Dwain G.]

Those leak detectors have been 're-discovered'. Many shops have bought new ones to help with late model engines that rely on oil pressure to operate features such as the phasers for Variable Valve Timing.

[dpson]

As a minimum pull the oil pan and see what the rod and main bearings look like. There are reports of a batch of bad bearings, likely from China, that came into the market about 15 years ago and were apparently sold by reputable parts vendors. I've personally seen what they look like after only about 5000 miles, worn down to the copper surface below the original bearing surface (see below).

[chet445]

I'm going to pull the engine and rebuild; I have done it before on 259s and 289s thus will really know about the engine. Quite a chore.

[dpson]

Keep us posted as to what you find out as to what might have caused the low oil pressure when you have it rebuilt.

[tsenecal]

I've been holding off on a response, because I didn't want to hijack the thread. I rebuilt my 289 about two years ago, and have the same problem. Around 40 cold, then not much over 10 psi warm. The block was bored, with pistons fitted at the machine shop. New cam bearings installed there as well. I checked ring gaps on each cyl, and plastigaged every bearing cap. I also put a new gear set in the oil pump. I added an aluminum timing gear, and had the rotating assy balanced to the new pistons. The block was hot tanked, and I cleaned all of the oil passages with a brush kit. The one thing I didn't do, is clean the rocker shafts. I hadn't come across that information on the forum until after it was built, and running. I'd like to thank Jack Vines for pointing that out occasionally here, I just happened to see it a little to late. Anyhow, my plan is to pull the engine back out this spring, and pull it apart to check condition of bearings, oil pump, etc, and clean the rocker shafts. I believe that I will rebuild a different oil pump also. I will also share what I find with the forum at that time. Wish me luck.

[PackardV8]

Best of luck to you both.

For a Stude V8 to have only 10 PSI hot means something in there is seriously looser than it should be. The good news is neither of you report any knocks or noises.

As has been mentioned, the most obvious place to look are the two plugs in the rear of the block. Those are all too often forgotten.

One instance of low oil pressure was traced to installing an incorrect rebuild kit in the oil pump. The '51-55 rebuild kit is different than the '56-64. Even with .025" too much clearance between the gears and pump body, that engine still held 25-35 PSI.

Even when the restrictor fitting is not installed in the bypass oil filter, it still holds more than 10 PSI.

Late rocker arms on an early shaft can lower oil pressure.

The incorrect undersize bearings (i.e. .020" bearings and a .030" crankshaft) will usually make enough noise to be heard.

jack vines