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View Full Version : Low oil pressure revisited



dpson
05-08-2007, 07:30 PM
When I started this thread last fall I got several good suggestions as to what might be causing low oil pressure in my 62 Lark. I ended up putting the car away for the winter before checking them out. Here's a recap: 62 Lark V-8 259 converted to 289, previous owner rebuilt engine, did much of the assembly himself, replaced main and rod bearings and plasigauaged them and got proper clearances, didn't replace oil pump but checked cover and gear clearances which were within spec., replaced the cam , not sure of the bearings. He used a lot of blue RTV to seal valve cover gaskets, etc. Oil pressure on strart up at high idle is around 25 lbs, as engine warms up oil pressure steadly drops to around 5 lbs at warm idle. When the pressure gets down around 5 lbs the needle on the pressure guage starts to bounce up and down a couple pounds in each direction quite rapidly.

Based on the advice from last fall here's what I've done so far this spring; pulled distributor and checked to see if the rear galley plug is there, it was, pulled and replaced oil pressure relief valve and cleaned around seat in the block, replaced aftermarket oil pressure guage with a different one, no change, changed oil to 20W-50, no help. Pulled right valve cover, every thing looks okay, however found some strands of blue RTV on the top of the head.

I figured I'll pull the pan next and replace the oil pump and check the strainer, etc. Any new thoughts/suggestions?

Dan Peterson
Montpelier, VT
1960 Lark V-8 Convertible
1960 Lark V-8 Convertible (parts car)
1962 Lark V-8 Regal Convertible

sbca96
05-08-2007, 07:51 PM
Its odd you got "no change" from using 20w-50. This was suggested as
a solution to my low oil pressure issue with my Avanti R1. I get a
nice 65 psi when its cold, but it drops down to 20 psi which makes me
a little uneasy. I can't even imagine ONLY 5 psi!! The change to the
20w-50 made a difference only when cold, but it was noticeable. I was
told that its probably cam bearings, but I have no idea the history of
the engine, considering the condition of a core plug I just pulled I
doubt its been rebuilt in its 102,000 miles.

I will be interested to read what others have to say. I would think
that the oil pickup strainer is clogged (with blue RTV) or loose on
the slip fit in your situation. Just a couple thoughts.

Tom

'63 Avanti, zinc plated drilled & slotted 03 Mustang Cobra 13" front disc/98 GT rear brakes, 03 Cobra 17" wheels, GM alt, 97 Z28 leather seats, soon: 97 Z28 T-56 6-spd, Ported heads w/SST full flow valves, 'R3' 276 cam, Edelbrock AFB Carb, GM HEI distributor, 8.8mm plug wires

gthawk64
05-09-2007, 11:52 AM
This is pretty obvious, but did you check the oil pump? I had some horrible oil pressure and after taking off the pan, replacing all the hoses, new filter, cleaning the strainer...I notice hey the oil pump cover is leaking.

I know the gaskets on the oil pump are paper thin. I used a very thin layer of gasket compound and I now have excellent oil pressure.

Could of been because I replaced the entire oil system though, but my money is on the oil pump having a small leak.

Mike '57 Transtar

Mike
05-09-2007, 04:52 PM
If it's a full flow engine, check the disc valves in the bolted on oil filter adapter, before you pull the pan. One is a relief valve that's supposed to open at 60 psi; and dump oil directly back into the crankcase through a 1/2" hole in the side of the block. It's right there on the oil pump output; and prone to failure. Some folks have had the valve actually fall out, when they changed the filter. A lot of them just leak badly. The pump can supply a moderate leak and show good pressure at higher speeds; but not at an idle. I suspect less oil goes through the pressure control valve to the timing gears when the relief valve leaks, too.
Mike M.

curt
05-09-2007, 06:14 PM
I never heard of the relief valve in the oil filter area, nice to know about this. Is it easy to replace? I do know of a Kaiser (Contenintal 6 engine ) that had 'jumping oil pressure needle'. I turned out to be a gasket between the oil pump and block was leaking . The leak resulted in one oil deprived main bearing. The engine was stopped, towed, diagnosed and fixed with a new bearing and new gasket.

skyway
05-09-2007, 07:12 PM
If what's been suggested does not turn up a problem, think about the bearing clearances. Do we trust the seller, or could there be some miles driven, or years sitting, on that rebuild?

Since you'll have the oil pan off anyway, go ahead and inspect and plastiguage the mains and rods. And pay attention to anything you find laying in the oil pan. I once bought an R-1 with acceptable oil pressure, that had allegedly bent a pushrod. I pulled the oil pan planning to check a rod/main or two, and found a big curl of cam bearing babbit justlaying in the oil pan. Turned out one of the cam bearings was missing quite a lot of its surface.

Note that cars with automatic transmissions can be especially hard on their middle mains.

If the original mains and rods had lost a lot of babbit to corrosion, or if upon inspection you find corrosion now (usually shows up as spalling or "snail trails"), I'd be real curious to inspect those cam bearings.

Also, cam bearings are often overlooked in a rebuild, and even if replaced, can easily be damaged on installation, damaged when installing the cam shaft, and/or incorrectly installed so that the oil supply holes do not match up.

Mike
05-09-2007, 07:36 PM
The oil filter adaptor bolts to the block with two bolts. It's easy to remove and check. Use a new gasket, and make sure the bolts aren't bottoming out, when you put it back on.
The second valve in it is a filter bypass. It has a much lighter spring - six pounds, I think.
Both the relief and filter bypass valves are simple discs with small coil springs behind them. They are held in the adaptor by steel rings that are just staked in the aluminum body. The adaptor was made, (cheaply), by an outside supplier.
I doubt either valve is really needed. Most filters have a bypass built in. The relief valve wasn't there on earlier, pre full flow, engines with the same oil pressure control valve at the front of the block. I'll probably remove the valves and plug mine if it fails again. I don't think Sasco has any new ones left.
I'll use a filter with a heavy case, like the K&N HP-2003; and be careful not to rev it with the oil cold.
Mike M.

dpson
05-09-2007, 09:38 PM
Thank you all for the thoughts and advice. To respond to some of your ideas, it's not a full flow engine, so the oil filter adapter idea is out (still good advice for others who might be in this situation). I absolutely trust the previous owner so far as the bearing replacement and fit, so there is no question in that regard. The car has been driven about 3000 miles since the rebuild.

I should also add that I bought the car with the full knowledge of the low oil pressure and the price was very fairly adjusted to reflect it.

Pulling the pan and changing the oil pump (without having the car on a lift) are not high on my list of fun things to do, but right now it seems like the next thing to try(other thoughts?).

Dan Peterson
Montpelier, VT
1960 Lark V-8 Convertible
1960 Lark V-8 Convertible (parts car)
1962 Lark V-8 Regal Convertible

Mike
05-09-2007, 10:01 PM
Not a full flow - so much for that idea!
You know, that oil pump will work backwards, too... If you improvise a way to feed kerosene into one of the plugs on the heads, and turn the engine over backwards, you can flush the pickup screen into the sump and out the drain plug.
If you had a canister type oil filter, (no, huh?), you could fill it with kerosene and push the car backwards, in high gear. Of course, you would have to plug the "out" port of the filter; and it's easier to move the car with the spark plugs out!
I'm faced with pulling the pan on my Stude, myself; and inclined to look for alternatives.
Mike M.

60ragtop
05-10-2007, 11:54 AM
I'd like to jump into this thread. I'm currently having the same problem as Dan. I just had an experienced restorer (with some Stude experience) rebuild the 57 289 in my 60 convertible. Pulling it in the garage, I noticed the oil light flickering. A gauge shows it pulls plenty of oil pressure cold on start up but drops to 10 when warm at idle, indicating something is expanding. Pressure comes up a little on revving the engine. The engine was rebuilt using the SI major overhaul kit and included new relief valve, lifters, oil pump kit, cam bearings, etc., etc. All the goodies. Rebuilt cam from Fairborn Stude. Runs fine except for the oil pressure problem which is (probably) contributing to some valve train noise. So far we've confirmed the relief valve is installed and working, the infamous oil gallery plug in the distributor bore is installed, and of course, there's oil in the engine. Next step is to pull the engine next week and do an air pressure test. Before then, the rebuilder wanted me to run this past the Studebaker gurus. He's thinking about this all weekend, as am I. He suspects lifters but hasn't run into a problem on v-8s only Champ 6's where oversize lifters were required. By the way, the engine had to be bored .060, so it was well worn, although I don't know the mileage or previous maintenance. Any ideas?

PackardV8
05-10-2007, 12:09 PM
Here are some wear areas I have found:

1. Rocker arms. They wear eccentrically, so the shaft assembly has to be sent to Rocker Arm Supply for rebuilding.
2. Oil pump body. Putting new gears in a body without confirming end play or side clearance.
3. Lifter bores. If the bores are worn oversize, rebushing or oversize lifters are both expensive propositions. Consider a reducer in the oil feed holes. If I remember correctly, Ted Harbit has done this on his racing engines.

thnx, jv.

PackardV8