C-1 oil pressure problem

[Larry Allen #11708]

After a complete rebuild of a '59 283/245 the oil pressure now reads over 60+ lbs. at anything above an idle. At idle, engine hot, it reads about 35-40. Prior to rebuilding the engine the oil pressure was normal. Since this problem surfaced I have done several things....1.attached a mechanical gauge to engine, read the same, pegged at 60#. 2. removed engine, checked for blocked oil passages, didn't find any blockage, had block boiled out. 3. checked all bearing clearances. 4. replaced oil pump with GM #10055849, a standard pump according to the parts guy. 5. replaced the distributor (the car came with a different distributor, I put the original back in during the rebuild. I know it doesn't help but I'm desperate.) 6. changed the oil filter bypass spring.

None of these things made any difference. I have 10w30 oil and have also tried 30w, with no change.

The question I have is there something I have missed that would alter oil pressure?

[Joe L.]

Re: C-1 oil pressure problem

Larry----

You've already taken all of the steps that I would have recommended. I'll think about it some more, though. In any event, I'm posting now to confirm that oil pump GM #10055849 IS the correct oil pump for your application. So, you needn't have any doubt that you have the correct one (asuming that the part in the box is what it says on the box). However, if you want to check the relief spring (which is VERY easy to do) your spring should have 21 coils and should be 2-7/32" free length. There should be NO white stripe on the spring, although there may be another color stripe.

[Chuck S.]

Re: C-1 oil pressure problem

Joe,

Aren't there some issues relating to interchangeability of the rear cam bearings for early small blocks? I seem to remember an article dealing with a design change in oiling holes, grooves, or something, such that if the incorrect bearing is installed, you get no flow through the bearing. Would such a reduction in total orifice area increase the oil pressure that much?

But, it seems Larry would have found a boogered cam bearing in his trouble-shooting tear down, if this were true.

Chuck Sangerhausen

[Chris H.]

Re: C-1 oil pressure problem

At the risk of sounding like an idiot, why is "high" oil pressure bad?

[Chuck S.]

Re: C-1 oil pressure problem

Chris,

In itself, high oil pressure isn't bad...it's good IF it is REAL and isn't being achieved due to malfunction. I think that's what Larry is concerned about.

In Larry's case, he rebuilt the engine to specification and now has oil pressure which may be high for what should be expected for the engine given the design bearing clearances, oil pump, etc. Thirty-five to forty may be a high for a hot engine at idle unless you have a high volume oil pump or tight bearing clearances. I claim to be no expert here, but I have seen about 20 psi under such conditions. That engine was in excellent condition, but was not freshly rebuilt. One racing engine (open clearances) I observed had 7 psi at idle.

Chuck Sangerhausen

[Dale Pearman]

Re: C-1 oil pressure problem

It's GOTTA be the spring in the oil pump. What else?

Varooom.

[Dale Pearman]

Re: C-1 oil pressure problem

I assume the distributor housing near the drive gear has a groove milled all the way around the casting. This provides oil for the galleries.

Varooom.

[Jeff]

Re: C-1 oil pressure problem

Is the line to the gauge sized properly? Is it kinked anywhere? Check the spring in the oil pump and swap it out with a softer one (only as a test). Are the bearing shells installed properly with oil holes where they should be?

JP

[Jeff]

Oil is very misunderstood and I feel for it...

... and high oil pressure is bad for several reasons. As Chuck said, if it is the symptom of a malfunction, particularly a blockage causing starvation in a different area, that is very bad. It also causes power loss which isn't too bad unless you are racing and looking for every HP 'to the ground'. It causes increased oil consumption (by throwing more oil up under the pistons than the oil ring can control), octane degradation, carbon deposits and prevents you from using oil of the optimum viscosity for your application.

Most folks think that the most power you will ever make with any given engine is running the thinnest oil that will properly lubricate that engine but that's not true. We always hear that oil does 2 things, that it lubricates and cools but that is only half right. It actually does 4 things, the other 2 being that it also seals and cleans.

Oil carries dirt, in suspension, to the filtering system and it seals combustion pressures into the combustion chamber. No two machined parts mate perfectly no matter how shiny and polished they look. Oil makes up the difference in those microscopic surface irregularities. An oil that is too thick can't flow into small crevices and seal properly (that's why running heavier oil to reduce oil consumption doesn't help and may actually hurt) and an oil that is too thin gets into those crevices but can't "hold its ground' and is blown out of place by the pressure of combustion above the rings.

If your oil pressure is already mechanically too high, then you may be forced to cure that fault with the additional fault of running a lighter but too thin oil which puts you into the negatively regenerating cycle of having your oil contaminated and diluted by combustion by-products getting past the rings. Then the oil gets even thinner and the whole deals winds pretty much straight into the dumper from there until your are oiling with a mix of gas and oil.

JP

P.S. Almost nothing ever needs its rings replaced. When an engine burns oil folks immediately say it needs rings but the fact is it usually needs bearings. The only reason new rings cures the oil consumption is that they usually replace the bearings while they have the pistons out to replace the rings. The old bearings, with their increased clearances, slung so much oil up under the pistons that no oil ring, new or worn, could have controlled it so it burned the excess oil. You get into the same situation, of having excess oil thrown out of the bearings, with high oil pressure but due to excessive pressure, not excessive clearances.

[Casey Andersen]

Re: C-1 oil pressure problem

Why not clean up and install the original oil pump? That would eliminate any question whether the pump is at fault or if it is a restriction in the oiling system. Casey Andersen

[Dale Pearman]

Re: Oil is very misunderstood and I feel for it...

Very interesting post Jeff. I would like to add that in creating higher than normal oil pressure, regardless of reason or cause, more horsepower (actually energy) is required AND the temperature of the oil rises. Both these facts are negative in just about any application.

I never cease to be amazed by the general misunderstanding of oil and bearing function by the public. Few of us realize that liquids can't be compressed and if we mantain a stratum of liquid between two surfaces, in this case the crankshaft and the bearing inserts, we can load this junction with great pressures and rotational losses are liquid dependent. Heck, an auto engine can run on WATER just fine. (for a limited time) Obviously, oil with it's additives, is a much better choice but the principles remain the same. Also, water dosen't work very well on cylinder walls! I've seen hucksters on TV with engines running add water to the lube system after treating the engine with whatever their product is, and the engines just keep on running. They would have done so even if not treated!

Varooom.

[Jeff]

Re: Oil is very misunderstood and I feel for it...

That's true, Dale. No one seems to understand that once you cross the boundary and reach dynamic oiling conditions NO wear whatsoever occurs at the bearing surfaces, that almost all wear occurs on start-up, with a very minor amount attributable to shutdown. As you say, that is how they are able to do all those TV commercials where they drain the oil and the engine keeps running.

I am also always amazed that folks get so cranked up over a little part throttle detonation, which never hurt anything (just back off a little bit or put your foot into it until it stops), but those same folks don't give a second thought about lugging that very same engine mercilessly.

Lugging, depending upon the engine speed at which it occurs, either causes the engine to fall entirely out of dynamic conditions or transition between low speed and dynamic lubrication. That is absolutely death to bearing surfaces because you now have the (totally avoidable) worst of both World's, the horribly wear inducing situation of having all the wear due caused due to the non-protection of low speed lubrication AND the added pounding of an engine under power as opposed to just idling on start-up. That is as bad as it gets.

JP

[Larry Allen #11708]

Re: C-1 oil pressure problem

When I first did the engine it had been rebuilt less than 10,000 miles before. All I did was check all the surfaces, clearances, replaced the seals (as ten years had passed since the initial rebuild by the previous owner) and I also replaced the distributor with the correct one. Nothing else in the engine was changed. On starting I had high pressure, I changed the oil, filter and the bypass spring in the filter. Still had high pressure. Then I removed the engine, boiled out the block, checked the oil passages in the crank, replaced the cam bearings and cam. I also replaced the old distribtor to see if that was it. No change, still 60# plus of pressure. At this point I replaced the oil pump and tried again. No luck. After driving the car for about ten miles I dropped the oil pan and removed all the main and rod bearing caps. Every surface was well oiled and still wet. I have not checked the cam bearings as they are not accesible from the bottom. Where do I try next?

[Chuck S.]

Re: C-1 oil pressure problem

Larry,

In your accounts, only three things happened/changed before you first observed 60 psi oil pressure: (1) disassembly and reassembly, (2) the correct distributor, and (3) fresh oil and filter.

Unless you have forgotten some detail, the problem has to be related to one of these. Since you later reinstalled the original distributor with no improvement, I think you can eliminate (2). You also changed the oil and filter again with no improvement, so you should be able to eliminate (3), UNLESS you have changed to a different type of oil or filter with the first rebuild, and continue to use these (I'm thinking mislabeled oil bottles, faulty fiter media or construction, etc).

When you had the block boiled out, I presume you had the shop remove the block plugs and rod out the oil galleries? Your engine doesn't have a replacement 265 block does it? (I have no idea if a 265 can be overbored to 283) Did you have good top end lubrication? When you installed the pistons, did you make sure the "notch" faced forward (Elementary, but my buddies, Wally and Beaver, ruined a freshly built racing engine THREE times before they figured out the notch went to the front). The main and rod inserts have notch detents, so they can't be installed backwards, can they? Did you use paper towels or cloth to wipe down the block interior and parts? (Thinking about tendency of paper towels to shed small pieces under stress, and possibly plug an oil passage) Just brain-storming here trying to give you some ideas.

If you are able to eliminate (3), and you can find nothing awry with the assembly on tear-down, I believe I would try to use a pressurized source (liquid would be better) to verify full oil flow through the main gallery down to the cam bearings, and through the lifter galleries to the top end. This would imply that debris or small fastener was introduced before/during your original reassembly, and I have no idea how that could happend. Sounded like you had already checked for good oil flow.

Good Luck.

Chuck Sangerhausen

[Larry Allen #11708]

Re: C-1 oil pressure problem

When I pulled the oil pan and removed the bearing caps I confirmed that all the bearings were installed correctly. Also, the pistons are facing forward. This is the original 283 .010 over. I can't find any area that is not oiling. The only two things left are as you say, the oil and filter. I am using the same type filter (Fram), I won't think that would be the problem but I'll try another type. Also I want to comfirm that the second gauge I used to check the pressure is accurate. I may have two bad gauges (I hope). I did use paper shop towels when I was working on the engine but it would take a lot of paper fuzz to block 60#+. But still a possibility. I'll try a lot things before I remove the engine again.