beanie

I'm hoping someone has some insight about possible causes for a peculiar oil consumption problem that I'm having with my '72 350. I rebuilt the engine .030 over, new pistons, rings, valves, guides, seals, seats, oil pump, cam and bearings, high vol. pump, etc. Quality parts, all as close to stock specs as possible. Heads and block were professionally done at a very reputable machine shop. After 10k miles, it was continually getting worse, using about a qt every 300 miles. All plugs were loaded up with carbon, all pistons are caked up as well. Hardly any smoke visible when running. No Leaks. Engine actually ran very smoothly. With the pcv valve out of the valve cover, it still used oil.
The engine is now apart. Oil rings have full contact in correct arrangement, with good drag in the bore. Compression and vacuum were good.
What am I missing? Any ideas?

oldcutlass

Are you sucking oil through the valve covers, vents, PCV? Was there any indication of any blowby?

beanie

Thank you for asking.
The carb and air cleaner are clean inside/out. I ran the car for about a week with the pcv valve removed from the valve cover and wrapped with a rag while still hooked to the base of the carb on its original location. The other valve cover has the orig filter that ties to the air cleaner.

rocketraider

Possible bad intake to heads seal. It will suck oil from the lifter valley past any gap and into the cylinder thru the intake valves.

That HV oil pump may be contributing too esp if you didn't use restrictors. Too much oil going to the valvetrain area and getting into the cylinders past valve seals and guides. Since all cylinders are like this I'd lean toward that scenario.

beanie

Thank you for you response.
I looked carefully at the intake gasket. It appears to have sealed okay. additionally, all of the cylinders had the same problem. I did the "propane in the oil system" test while it was running with no change in rpms.

The oil pump suggestion is interesting. If I'm not mistaken, the lifters are the limiting factor as to oil delivery to the top of the heads. If aftermarket lifters has can pass a greater amount of oil than the stock ones did, does it make sense that the oil could well up at the guides? I don't know how restrictive the drain passages are. They do seem small to me. I did notice that they are not much lower than the top of the guides, which would make me believe that it wouldn't take much to flood them over, below the umbrella seals, and suck through to all of the comb. chambers.
Ive never heard of anyone regretting using a HV pump. Are Olds engines more fussy about this?

oldcutlass

What were your compression test numbers, did you do it both dry and wet? What kind of vacuum did it pull?

beanie

To be honest, I tested vac and comp, but I can't say for certain what the numbers were. It was a while ago. I remember both were excellent and I dismissed them right away.

oldcutlass

Based on what your saying, the only things I can come up with are, valve guides, piston to cylinder wall clearances, ring issues of some sort, cracked intake plenum...

Greg Rogers

I remember back in the 80's when the 70's cars were getting older there was many times when older high mileage Olds v-8's were smoking/using oil and you would take off the valve covers and they would be all gunked up. The oil drain back holes were clogged and the oil would get sucked into the combustion chambers thru the intake valve guides. In that situation they usually leaked alot of oil from the valve cover gaskets also. We would run wires down thru the holes and and clean it up and replace the gaskets and it was acceptable then for a old engine. I don't know if a high volume oil pump could do it but maybe. Are your valve guides/seals ok?

beanie

Yes, the valves and guides are with correct clearances.

Octania

Repeat after me:

"A High Volume oil pump DOES NOT force more oil thru the engine."

The HV oil pump is CAPABLE of supplying more oil to the engine. Did we not just go over this again?

Yes: https://classicoldsmobile.com/forums...-oil-pump.html

"The "HV pumps suck the pan dry" myth is right up there with "headers won't fit Supremes". I've run one on a street-strip car with no problems whatsoever. The only time you'll POSSIBLY have a problem is if this is a high mileage motor with all the oil return holes coked up - and if THAT'S the case, you have a bigger problem."

"I ran a stock pan for many years with the HV pump and NEVER pumped the pan dry."


The actual flow of oil at pretty much any engine speed over idle is controlled by
Pressure as set by the relief spring in the pump
Oil viscosity
Engine clearances

Pumping more oil faster AT THE PUMP does not cause more to accumulate in say the valves area. ANY time the pump output exceeds the flow thru the engine... the excess production never makes it out of the pump.... it dumps across the pressure relief back to the pump inlet side.

This will be the case at pretty much any engine speed over idle.

One good reason to use the HV pump is if you have purposely set up your engine with generous loose bearing clearances, to allow more oil flow, which provides more cooling and cleansing of the bearing areas.

Again:

A High Volume oil pump DOES NOT force more oil thru the engine.

If you are flooding the valve area, you need to fix the drainback issue. Taking a peek at the conditions under the valve cover after a brief higher-rpm term should clarify if that is happening.

beanie

Thank you Mr. Octania for your condescending response. I am new to this forum process, and have not had a chance to read all of your profound and insightful information.
By the way, no one mentioned anything about "sucking the pan dry". And as I mentioned, this is a freshly built engine. None of the holes are coked up.
I don't believe you have much to offer that I wish to "repeat after you".
To everyone else...I appreciate your help.

oddball

Octania's post may not have been directed at you....!

I'd bet money that it's either valve guides or intake seal. If you have oil in the intake all the way up to the plenum, then it's almost certainly intake seal. If it's more localized to the intake runner, then valve guides. My 350 is on a stand waiting for a refresh, and it's in the same state. 1qt every 300 miles, and it's the valve guides.
There's not much of a "spec" for valve guide clearance. Most shops just hone by feel, and there's obviously room for error there. The stock umbrella seals don't help.
Intake sealing is tricky. I've R&R's intakes at least 20 times and just now getting a good, repeatable process. Being able to accurately evaluate the alignment is tough, too. These engines can easily suck up oil between the intake and head without showing any other symptoms (good vacuum, propane test negative, etc).
I'm not insulting your machinist, but they may not know the peculiarities of the Olds engine. The intake seal and the valve guides are more particular than a Chevy.

rocketraider

Chris, I respectfully disagree. Pressure and volume of flow are two separate things. If an oil pump relief valve is set to maintain a certain pressure, that is what it will do. A high volume pump will pump more volume of oil regardless of where the relief valve is set. Using a high volume pump it is very possible to overfill the valvetrain area especially if the drainback system is compromised or has not been modified to handle excess volume of oil.

I think OP's oil consumption problem is in the valvetrain area. Either the intake did not seal properly and the engine sucked oil in thru the intake ports, or it's a valve seals/guides issue. Beanie, did you notice a lot of crud on the intake valves?

droldsmorland

X2 if the plugs and pistons are caked the oil is most likely getting past the valve seals. Do you get a puff on start up? Or you have an oil control issue with the rings. Have you pulled the rocker covers to see if the seals are OK? You don't have bee hive springs on those valves do you?

MDchanic

This high-volume thing is geting to be like a recurring nightmare.

I will lay this out, in accordance with the immutable laws of Classical Physics.

A high volume oil pump has a longer chamber containing longer gears, which are the part that does the pumping, so it is capable of pumping more oil per revolution (higher volume).

The dimensions of the oil pump do not change, and oil, like any fluid, offers resistance to being pumped, so, since the high-volume pump pumps more oil per revolution, it is harder to turn, and takes more power from the engine to operate, at all times.

In a situation where there is no resistance to oil flow past the pump (like if you had it connected to a drill in a tub of oil), the high volume pump will consistently pump more oil (higher volume) than a regular pump, and both will pump more oil than they would if they were pumping oil through a restriction.

In a situation where there is resistance to flow after the pump (such as installed in an engine), the pump will develop a pressure head that is proportionate to the amount of resistance and the speed at which the pump is turning.
Little resistance and/or low speed will equal lower pressure.
High resistance and/or high speed will equal higher pressure.
You can read the pressure on your car's oil pressure gauge.

Additionally, oil gets thinner as it gets warmer, making it flow more easily.
This makes it easier to pump, and makes it require less pressure to get through smaller spaces.
Using oil of lower viscosity ratings will have the same effect.

In general, if the thickness of the oil and the speed and capacity of the pump are the same, higher pressure will be an indication of greater resistance to flow, and therefore of less oil actually being pumped.

So, in a motor with certain clearances, at a given speed and pressure and with oil of a given viscosity, a pump of a certain capacity will develop a certain pressure.

Increase the clearances (worn bearings, or race-set clearances) and the pressure will drop and the flow will increase, all other things being kept equal. Decrease the clearances pressure will increase and flow will drop.

Similarly, decreasing the speed of the pump (which is to say, the RPMs of the engine) will drop the pressure (and the flow) and increasing RPMs will raise both.

Now, it happens that if you want adequate pressure at 500 RPM, your pressure at 5,000 RPM would be through the roof, which would require a bunch of engineering considerations, and would probably create so much resistance in the pump that the engine would lose a great deal of power.
Because of this, your oil pump is equipped with a pressure relief valve, so that the engineers never have to worry about designing for pressures over a certain amount (seems to be about 40 or 45psi), or power loss over a certain amount.
Once your oil pump gets to its set pressure, the relief valve spring will begin to compress, allowing the relief valve piston to move through its bore, opening an alternate route for the oil to take right back to the oil pan.

So what's my point?
No matter how much potential your oil pump has to pump oil through your engine, it will only pump the amount that will flow at its maximum set pressure. Above that, the excess pressure and volume will be blown off right back to the pan.

A high volume oil pump will provide more volume at low RPMs, when a low-volume pump might be maxed out, so you might notice your oil pressure gauge staying at its maximum set point at lower speeds when the engine is hot. This is probably good.
Once the RPMs go up, though, the relief valve will open (sooner for a high volume pump, later for a regular pump, but it will open for both) and excess oil will be bled off to the pan, and will never get into the engine's oil galleries, its lifters, or its valve gear.

If a high volume oil pump had no pressure relief valve, then, yes, it would force additional oil up into the engine at higher RPMs. It would also take 50 HP to turn, require a drive shaft and gear that looked like agricultural equipment, and get really hot.
Since your oil pump DOES have a relief valve, none of this happens, or ever can happen, and the maximum amount of oil that can be pumped is proportional to the maximum pressures achieved, no matter which pump is creating those pressures.

- Eric

oldcutlass

My problem is with all pistons caked and plugs loaded with carbon statement. I can see a pair side by side, or a whole bank, left or right. But the OP states all.

So outside of an assembly issue, mismatch of parts, a major failure in rings (has no blowby or excessive smoke) , valveguide seals and or guides. A cracked intake plenum that would suck oil and distribute to all cylinders. I just can't think of anything else.

Rickman48

Is there a possibility the compression rings are upside down?
Cadillac made that mistake on the 1st 2000 cars off the line, in 67, so it could happen to anyone. [24 hr. warrantee time!]

beanie

Thank you all very much. Let's see...
Yes, there is a great deal of build up on the back side of all of the intake valves.
I did verify that the ring configuration is correct.
I have not verified that the intake manifold does not have a crack, but prior to the initial rebuild the engine had no signs of significant oil use when I tore it down and supposedly ran fine. The rebuild was done only as preventative medicine.
Up until now, I have had umbrella seals in place, but I am in the process of installing fixed seals.
No smoke puff at start up, and very minor evidence of smoking while going down the road. The odor is the biggest give away.
The springs are stock.

I'm beginning to think that the new fixed seals, and possibly opening up the drain passages might be the way to go.
The problem I have is that I can't find the smoking gun---with certainty.

As I have said, thank you all for taking time to put your minds on this problem. If I find the answer as time goes on, I'll post it for future reference. Any more suggestions? I'll roll those around, too.

-Mike

jpc647

For us youngin's can you explain what this is? I googled it, but did not come up with anything.

beanie

After a very thorough and methodical complete rebuild (second time) w/ new pistons, rings, rod bearings, timing chain, std. vol. oil pump, fixed stem seals, mild cam w/ lifters, complete gasket set including turkey pan type intake gasket.....etc., ....the oil consumption problem has been eliminated. The question remains...WHY?
Hastings rings were found to be installed properly with good drag and seating. Proper end gap. Felpro umbrella stem seals were all on correctly (as originals). The high vol oil pump should not have been a problem, but was replaced w/ std vol (out of frustration more than anything). The intake gasket appeared to be sealing all places it should have. The new one is identical. The heads were untouched other than the new seal design. Quality oil w/high zinc/phospherous content is in it now.
After about 300 miles and 15 hrs run time, it idles at about 1000 rpm hot w/50 psi oil press.
Any ideas?

oldcutlass

Glad all is well. None of us had any real direction as yourself as to a cause or cure short of what you did. It had to be something common to all cylinders.

Octania

Must have been that HV oil pump!

*JUST KIDDING*

Glad to hear it's all better now. My vote would be for ring installation or seating problems. It's all water under the dam now though.

btw, MDchanic, thanks for the superb treatise in oil pump, flow, and pressure. One teeeeensy correction:

"Once your oil pump gets to its set pressure, the relief valve spring will begin to compress, allowing the relief valve piston to move through its bore, opening an alternate route for the oil to take right back to the oil pan."

The Olds oil pump relief valves release the oil to the INLET SIDE of the pump- one notch more clever than dumping to the pan. Why run it thru the pickup screen again? I remember when I discovered this, I thought it was exceedingly clever.

Oh, and beanie, there was no condescending remark directed YOUR way, just insight for those in general who subscribe to the theory that somehow a HV oil pump "causes" excess oil in the engine upper end.

MDchanic

I did not know that.

Thank you.

- Eric

beanie

Thank you everyone.

Sampson

I am curious about your valve springs. I used a comp cam cam kit with my build and the umbrella seals would no longer seat correctly. Something to do with the inner spring. My engine guy caught the problem when he was putting the heads back together. He had to machine the heads for fixed seals.

beanie

Well, I'll be honest. I never planned on using umbrella type seals w/the new springs that are now in place. I can't honestly tell you if they would have worked or not. In your case, I would imagine that the inner dia of the of the inner spring must be too small, but i'm guessing. I will tell you that the retainer style had to be changed to accommodate the fixed seal in my engine.

Lady72nRob71

I think you will be happy with the stock umbrella seals.
My experience with the fixed ones is that they wear around the valve stem hole and deteriorate with age so that they need replacing every 8-10 years or so due to oil burning.

Sampson

[QUOTE=beanie;561729]Well, I'll be honest. I never planned on using umbrella type seals w/the new springs that are now in place. I can't honestly tell you if they would have worked or not. In your case, I would imagine that the inner dia of the of the inner spring must be too small, but i'm guessing. I will tell you that the retainer style had to be changed to accommodate the fixed seal in my engine.[/

They had to change the retainer style on my engine heads as well. And you are correct the problem resulted from the diameter of the new inner springs not allowing enough clearance for the umbrella seals. I was wondering if it was possible that you had the same issue and the umbrella seals were not seating because of clearance problems with the springs?

beanie

They didn't hang up in the stock springs. Good thought though.