1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

[Joe L.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Joe,

Whether it comes from a pcv valve or a leaking intake, it still has to pass the intake valve, which is what I described as one of the two ways for oil to enter the combustion chamber. Through the top or through the bottom.

No disrespect intended. We are all products of our own experiences. In mine, however, oil coming from a leaking lower edge intake gasket would be a real rarity. In 40 some years of doing this professionally, I have never personally encountered it. I don't deny it's a possibility, however the accompanying vacuum leak would produce a driveability problem much more obvious and troubling than the oil consumption. If it can pull a quart of oil splashing around in the valley in 300 miles, imagine how much air it would pull. And when I consider the amount of crush in those composite intake gaskets that GM used (as opposed to steel shim gaskets used by others), the amount of difference in the angles would have to be great enough that it would be visually evident when viewing the mating areas from the exterior front.

As to a PCV possibility, again, something I've never seen and have difficulty envisioning how liquid oil would get to the end of the PCV valve. I have seen the cyl head drains plug up (not on a Chevrolet built engine), but even in that case the issue becomes oil consumption through the guides because the seal's design is to shed oil, not seal it. So again, it first manifests itself as a guide/seal issue with the head flooded rather than a pcv issue.

So if we start first with the 99.99 percent of the time, it's cyl walls and valve guides. And I've seen enough valve guides taken out in very short order from dry assembly and wrong push rod lengths for the cam being used that I'm never very quick to rule out those things. And dirty cyl walls a common enough occurrence that the ring manufacturers include a notice in their packaging.

As an aside, the only time I've seen wet runners is super and turbo charged engines, leaking from their respective seals.

Steve

Steve-----


Yes, you're correct that the oil has to ultimately enter the combustion chamber through the valve guides or past the piston rings.

I also agree with you that if oil were leaking at the intake manifold gasket bottom there would also be a major vacuum leak. However, I think the oil, itself, would partly ameliorate this. I also agree that it would SEEM LIKE the amount of crush on the intake gaskets would seal even if there was an angularity problem between the manifold and cylinder heads.

However, I can tell you that I tried EVERYTHING to solve this problem on a small block once-upon-a-time. I changed intake manifolds at least twice. I changed reconditioned cylinder heads for brand new GM heads. I used every style valve seal available, from stock 0-ring to all teflon positive seals to Viton positive seals to umbrella seals. I used several different types of manifold gaskets from stock-type GM to several aftermarket types. I used different sealers on the gaskets from RTV to special aerospace sealers not even available in retail stores. NOTHING worked. Each and every time after trying something I got about 300 miles per quart of oil. Each and every time when I removed the intake manifold the intake ports in the heads right from the intake manifold interface were wet with oil and I mean WET. There was also considerable oil in the intake manifold passages. There's just no way I can conceive of that the intake ports could be wet with oil if the source of the oil were the valve guides/seals or the rings.

By the way, in desperation, I finally re-ringed the engine, de-glazing the bores, carefully cleaning them, and installing new rings. I didn't really expect this to work but I was desperate. It did not change anything---right back to 300 miles per quart. Also, this was definitely not a turbo or supercharged engine. It was a naturally aspirated, 4 barrel carb engine which was not even run hard, at all. It was built up from a factory new GM partial engine (short block) assembly.

I'm kind of surprised that you have not encountered this in all your years. Others have reported similar problems here on this board. In fact, at least one I seem to recall, posted pictures of intake ports wet with oil.

So, as I previously mentioned, if one finds the intake ports and manifold runners wet with oil, I do not see how the source could be valve guides/seals or rings. However, if there is no evidence of oil in the intake ports or manifold runners, then the source has to be valve guides/seals or rings.

[Steve G.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Joe,
In my experience,oil in the intake runner is not unheard of, getting there past the gasket is. When an intake valve is closed the bottom of the guide is exposed to the vacuum produced by all the other cyls. It is not affected only by the vacuum from it's respective cyl. I've always been of the opinion that this is what causes the migration into the intake.

Your experience is certainly an interesting one, but I think we can agree that incurable oil consumption issues, relative to the curable, represent an extremely small percentage. Small enough that I would suggest to the OP that he applies the rules of thumb that we have used in the industry since long before we had access to cameras that would let us look inside. Truthfully, I'm not convinced that looking inside will actually give any answers anyways.

My 2 cents on valve seals. I don't advocate and never use positive seals unless the engine came that way from the factory. I see only benefits to guide life from the bit of oil that makes it down the guide to an umbrella type of seal.

Steve

[Domenic T.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Steve,
In the 70's I was a mechanic at a dealer and the service writer sold a SB rebuild, so I pulled the engine after seeing it was blowing lots of oil.
Didn't have valve problems or ring problems or the leak as Joe described. when I finished I shook the pcv valve no action. I cleaned it and it worked, BUT the fact that the engine wasn't breathing caused the engine to build up presure and blow oil past the rings. The hose was also clogged up from the pcv not operating. I plugged the new hose to showed the service writer and bingo the car blew smoke again. put a new PVV and hose and all was good.
I also restored a British 500 single motorcycle that used the breather to oil the chain. Well I always had to clean the rear rim and spokes so I decided to buy chain lube and get rid if the breather. The breather also had a flapper valve like to the PCV. Got on the long Beach freeway and a car passed me and pointed to the back of my bike and there was a smoke screen that blinded any one behind me. there was so much oil in the cylinder that I had to put a clean plug in the bike to start it, all after I unplugged the breather and that was the end of the smoke screen.
Since then before I tear down a oil burner I check the engine breathing. Found a down draft tube on a SB that was smashed and caused oil burning.
Doubt that this is his problem but things happen. The method you described was one of our first tests to check the guides and rings so we had a direction to go.
Another problem back in the 70 were the chrome rings. Great rings but for grandmas car. we had one after the come in for waranty because of the rings not sealing on a new car. A buddy in a rebuild shop said to run the engine hard and it would seat the rings and that worked right away.

Dom

[Steve G.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

All this discussion brought back another memory of a situation not unlike Joe's. A fresh rebuild on a sbc and the engine using excessive oil. Mechanic was on the right track, narrowed it down to oil coming through the guides. Replaced the o-rings on the stems. No change.

We got it and pulled the springs and every o-ring was cut. He had been installing the o-rings wrong, putting them on the stem then pushing the spring retainer on past them and cutting the rings when he did it. He was not familiar with the static seal/umbrella arrangement used on sbc so he installed the "seal" like he did on any other engine.

I guess I never had an engine where the pcv was non op long enough to cause oil consumption. The only thing I ever saw was oil vapour coming out the make up air breather. Either an non operating PCV or an engine with excessive blowby, more than the PCV could consume.

Steve G.

[Domenic T.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Steve we are on the same page. umbrella seals with the O ring properly installed gets me about a quart burn in a 1000 miles. Also those positive seals do not lubricate the guides enough and when I do a valve job I find more problems with the guides and valve stems with the positive seals. I was told at the dealership that the complaint they got the most was oil and people did not want to add it every 1000 miles or lift the hood to check it. Now most new car owners can't even find the dip stick. Gone are the days when the gas station attendant raised the hood to check the oil.

Dom

[Joe L.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

All this discussion brought back another memory of a situation not unlike Joe's. A fresh rebuild on a sbc and the engine using excessive oil. Mechanic was on the right track, narrowed it down to oil coming through the guides. Replaced the o-rings on the stems. No change.

We got it and pulled the springs and every o-ring was cut. He had been installing the o-rings wrong, putting them on the stem then pushing the spring retainer on past them and cutting the rings when he did it. He was not familiar with the static seal/umbrella arrangement used on sbc so he installed the "seal" like he did on any other engine.

I guess I never had an engine where the pcv was non op long enough to cause oil consumption. The only thing I ever saw was oil vapour coming out the make up air breather. Either an non operating PCV or an engine with excessive blowby, more than the PCV could consume.

Steve G.

Steve------


As far as valve guides and seals go, I tried it all. I initially assembled the engine using a new GM partial engine assembly but with reconditioned original heads. These heads had all the valve guides replaced with thick wall replacements and several valves were also replaced due to stem wear. I assembled the engine with stock o-ring seals installed properly ( I learned from a mistake in this regard made several years earlier and as you described) and with stock valve spring oil shields. A quart in 300 miles.

I next installed o-rings seals and added umbrella seals. A quart in 300 miles.

I removed the heads and had the valve guides machined for positive seals. Installed all teflon positive seals (using seal protector sleeve when installing the seals over the valve stems). A quart in 300 miles

I figured my trusty an dependable machine shop had let me down with the valve guide installation. So, I purchased a new set of GM heads with all new GM valves, springs, etc. and installed stock o-ring seals. A quart in 300 miles.

I removed the heads and had them machined for positive valve seals. I installed all teflon positive seals. A quart in 300 miles.

I removed the all teflon seals and installed Viton seals. A quart in 300 miles

I installed 3 different intake manifolds. A quart in 300 miles each time.

I installed multiple different intake manifold gaskets and gasket sealers. A quart in 300 miles each time.

I re-ringed the engine after carefully de-glazing the cylinders and thorough cleaning of the cylinder walls. Installed Perfect Circle moly rings. A quart in 300 miles.

After each and every of the above steps, the one thing that remained constant was very oil wet intake ports in the heads and the intake manifold runners. I just don't see how any problem with the valve guides or seals could have caused this. I certainly don't see how any problem with the piston rings could have caused this. Also, the fact that I installed brand new cylinder heads with all new valves and stock valve seals pretty much eliminates the possibility that the problem was valve guide or valve seal related.

So, what did cause the problem? I never found out. It beat me. I gave up. One of the few problems I could never solve. I still have the engine, though. One of these days I'm going to carefully disassemble and "autopsy" it.

[Domenic T.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Steve,
I probably mislead about the pcv but it was not sucking oil. It was totaly clogged to the point that the engine couldn't breath and built up crank case pressure that blew oil past the rings. The carb was not sucking fumes at the VC thru the PCV. The engine hadanti spark plug fouwlers on it also to reduce spark plug foueling.

[Chris G.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Ok, so this is allot of information to digest. It seems that valve seals/guides may not be the issue. Problem appears to be much bigger and complex. Intake manifold fit to the heads? It still sounds like I have to find a way to see if there oily intake ports? Could that really cause all 8 cylinders to be burning oil? All 8 spark plugs seem wet with oil. From hearing about other stories here, now I'm worried there is a possibility it can't be fixed!

[Joe L.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Ok, so this is allot of information to digest. It seems that valve seals/guides may not be the issue. Problem appears to be much bigger and complex. Intake manifold fit to the heads? It still sounds like I have to find a way to see if there oily intake ports? Could that really cause all 8 cylinders to be burning oil? All 8 spark plugs seem wet with oil. From hearing about other stories here, now I'm worried there is a possibility it can't be fixed!

Chris------


I'd like to see photos, especially closeups, of the intake ports in the heads and the runners in the manifold. It's my opinion that if you find relatively large amounts of raw engine oil in these areas, then the problem is something other than valve guide/seal or ring problems.

As far as a solution to the problem if the above is what you find, I wish I knew the answer. Once-upon-a-time I tried mightily to find an answer but never did.

[Paul O.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Just a shot in the dark but when the engine was rebuilt did they mill the heads for straightness? If so and by how many thousands. Were the heads milled and rebuild at an earlier date also? At a certain amount of milling of the heads the intake must also be milled as the proper alignment of the intake and head ports angle is incorrect and oil will be drawn in to the port going to the combustion chamber. The gasket can not make up the angle difference between the head and intake.

[Paul Y.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Just a shot in the dark but when the engine was rebuilt did they mill the heads for straightness? If so and by how many thousands. Were the heads milled and rebuild at an earlier date also? At a certain amount of milling of the heads the intake must also be milled as the proper alignment of the intake and head ports angle is incorrect and oil will be drawn in to the port going to the combustion chamber. The gasket can not make up the angle difference between the head and intake.

That is exactly what happened to my 71. I tried all of the above and changed intake manifold gaskets 5-6 times using thicker and thicker ones. Finally I put the intake on the block without gaskets and the ends were touching with the top of the sides of the intake and the bottom did not touch. A friendly machine shop set up a jig and cut several thousands off the ends of the intake bottom. It solved the problem as oil was pulled into the intake runners from the mismatched bottom of the intake sides. I only could assume that someone had milled the heads and not matched up the intake therefore creating the vacuum leak which could not be found from the top anywhere. I just can chalk it up to running down a check list of things until you find another one that you may not even knew existed. The motor came to me that way and was built by a speed shop down in New Mexico. There fore I am in agreement with Joe L. as he was giving me good direction on what to check at the time.

[Joe L.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

That is exactly what happened to my 71. I tried all of the above and changed intake manifold gaskets 5-6 times using thicker and thicker ones. Finally I put the intake on the block without gaskets and the ends were touching with the top of the sides of the intake and the bottom did not touch. A friendly machine shop set up a jig and cut several thousands off the ends of the intake bottom. It solved the problem as oil was pulled into the intake runners from the mismatched bottom of the intake sides. I only could assume that someone had milled the heads and not matched up the intake therefore creating the vacuum leak which could not be found from the top anywhere. I just can chalk it up to running down a check list of things until you find another one that you may not even knew existed. The motor came to me that way and was built by a speed shop down in New Mexico. There fore I am in agreement with Joe L. as he was giving me good direction on what to check at the time.

Paul------


In my case, I had the same problem as you described with the ends of the manifold contacting the block. This was first evidenced by the "squeezing out" of the end gaskets. I had the manifolds I installed milled on the ends to correct this. However, that did not resolve my oil problems. I still believe, though, that the condition described above is a symptom of the basic problem underlying the oil burning. Just what it is, I don't know.

My GUESS, though: it is somehow related to improper block deck machining which occurred at Flint for the new GM short block assembly I used for this engine. I might be able to discern just what it is when I someday "autopsy" the engine.

[Joe L.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Just a shot in the dark but when the engine was rebuilt did they mill the heads for straightness? If so and by how many thousands. Were the heads milled and rebuild at an earlier date also? At a certain amount of milling of the heads the intake must also be milled as the proper alignment of the intake and head ports angle is incorrect and oil will be drawn in to the port going to the combustion chamber. The gasket can not make up the angle difference between the head and intake.

Paul------


In my case, the original heads I installed had been milled but only enough to ensure they were straight and flat. I do not know, though, just what the cut was. However, the second set of heads was brand new GM and un-milled.

[Mark E.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Chris,

I was reading threads about valve stem seals, and saw this one.

It's been over a year since your last post. Did you fix the oil consumption problem? Its cause?

[Chris G.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Hi Mark,
Thanks for the inquiry. Yes we did resolve my oil consumption problem in my 70 454. We had to replace all the valve stem seals, most were completely disintegrated except for a small black piece with a metal ring left. We were able to replace them all with the heads still on, by moving each piston all the way up or pressurizing the cylinder in case the valve dropped. I did notice a few times in the past years removing the valve covers and seeing broken black pieces sitting I the corners and always having oily spark plugs.