Big Block oil consumption problem with pics

[G A.]

Need a second opinion.
Motor was overhauled about a year and half ago. Stock stuff, new everything except castings. This includes guides, valves and seals. Iron guides but I'm not sure what the seals are (last two pics are of the seals). Engine has about 800 miles and has not stopped using oil. About a quart per 300 I'd say. No noticeable smoke when driving and none on start-up. Engine was OH'd before I purchased the car, shop didn't log the type of stem seals on the invoices I have. They are 6 states away.
I brought home a bore-scope from my maintenance department (not automotive maintenance) to look inside the intake runners hoping to find oil in them. No such luck. So went on and stuck the camera down in the heads to peek at the intake valves and this is what I found. My hope is this burned oil buildup is not bad enough to warrant removing the heads and I can just replace the seals, IF that's the problem. What thinks you??
Also took a shot of the #1 piston crown and also the "seals" on the valve stems. My feeling is the engine shop installed some kind of high-tech seal that either doesn't work properly or was improperly installed. I haven't built an engine in over 25 years, so I either don't recognize these seals or forgot that I should recognize them : ). I suppose we can still get the umbrella style that GM used? If so, who makes the best, highest quality umbrella?

These are from 4 different cylinders. All other intakes look essentially the same.





The guide seals.



#1 Piston crown

[Carl B.]

Re: Big Block oil consumption problem with pics

It looks like teflon seals they come in two sizes comp cams has them check the plugs for oil fouling also take compression test to determine probable cause of oil problem if you determine seals are the problem remove valve springs for suspect cylinder and measure guides and seals also springs are different umbrella seals won't work

[G A.]

Re: Big Block oil consumption problem with pics

It looks like teflon seals they come in two sizes comp cams has them check the plugs for oil fouling also take compression test to determine probable cause of oil problem if you determine seals are the problem remove valve springs for suspect cylinder and measure guides and seals also springs are different umbrella seals won't work

Static(?) compression is 247 psi across all cylinders (243-251). 5 rotations with the starter at each cylinder. Plugs have oil on threads. Electrodes are white to gray-brown and free of oil. What kind of seals will work? Why won't umbrellas work?

[Carl B.]

Re: Big Block oil consumption problem with pics

looks like teflon seals they come in two sizes check compression for possible oil problem and check plugs for oil fouling if seals are suspect remove valve springs from suspect cylinder and measure seals and guide and valve stem also valve springs are different umbrella seals won't work comp cams has teflon seals

[Carl B.]

Re: Big Block oil consumption problem with pics

sorry for double post

[Joe L.]

Re: Big Block oil consumption problem with pics

Static(?) compression is 247 psi across all cylinders (243-251). 5 rotations with the starter at each cylinder. Plugs have oil on threads. Electrodes are white to gray-brown and free of oil. What kind of seals will work? Why won't umbrellas work?

Dan------


The seals do look like the all teflon type positive seals. These should work ok. You can switch back to the stock type if you wish. However, as Carl mentions, you may have to change the valve springs depending upon what valve springs were installed by the rebuilder. If they are stock size and configuration springs, you won't have to change them. Otherwise, you might. A complete set of stock valve springs is available under GM #12371061 if you need them.

The umbrella valve seal used with the above springs is an umbrella shield which is integral with the valve spring cap (retainer). It's GM #3964264 and remains available (for about 15 bucks, each, GM list). These things used to be supplied as part of a spring package which included a spring and cap under GM #3970627 but it's now discontinued.

I think it's worth a try to change to the stock type seals. However, I don't think it's going to solve the problem because I don't think that the valve guides or valve guide seals are the root of your problem.

I think the root of the problem is one of 2 things:

1) A sealing problem at the lower side of the intake manifold gaskets causing oil to be drawn into the ports (even though you can't see this with your internal inspection), OR;

2) Oil being drawn into the intake manifold via the PCV system.

I've never found a reliable, "bullet-proof" solution to either of the above problems which plague both small block and big block Chevrolet engines.

[G A.]

Re: Big Block oil consumption problem with pics

Dan------


The seals do look like the all teflon type positive seals. These should work ok. You can switch back to the stock type if you wish. However, as Carl mentions, you may have to change the valve springs depending upon what valve springs were installed by the rebuilder. If they are stock size and configuration springs, you won't have to change them. Otherwise, you might. A complete set of stock valve springs is available under GM #12371061 if you need them.

The umbrella valve seal used with the above springs is an umbrella shield which is integral with the valve spring cap (retainer). It's GM #3964264 and remains available (for about 15 bucks, each, GM list). These things used to be supplied as part of a spring package which included a spring and cap under GM #3970627 but it's now discontinued.

I think it's worth a try to change to the stock type seals. However, I don't think it's going to solve the problem because I don't think that the valve guides or valve guide seals are the root of your problem.

I think the root of the problem is one of 2 things:

1) A sealing problem at the lower side of the intake manifold gaskets causing oil to be drawn into the ports (even though you can't see this with your internal inspection), OR;

2) Oil being drawn into the intake manifold via the PCV system.

I've never found a reliable, "bullet-proof" solution to either of the above problems which plague both small block and big block Chevrolet engines.

Joe,

The PCV is housed in the original valve covers, so trying to be optimistic here, I would expect that the issue would lay elsewhere. However, I'm no expert.
I can't rule out the manifold/head interface. I would have expected to see something noticeable in the runners though (?).
In the absence of someone going "yep I know exactly whats wrong", I may do both the intake gasket and seal change.
Dan

[Joe L.]

Re: Big Block oil consumption problem with pics

Joe,

The PCV is housed in the original valve covers, so trying to be optimistic here, I would expect that the issue would lay elsewhere. However, I'm no expert.
I can't rule out the manifold/head interface. I would have expected to see something noticeable in the runners though (?).
In the absence of someone going "yep I know exactly whats wrong", I may do both the intake gasket and seal change.
Dan

Dan------


One of the problems I've long-suspected is that even with a PCV system in perfect operating condition, original configuration and all new system parts, this problem can occur. That's one of the reasons I've not been able to come up with a solution to it.

When you remove the carbs, check the plenum under the center carb (into which the PCV hose connects into the manifold). Check carefully to see if there is a greater evidence of oil film/residue than there is in the plenum under the other carbs.

[G A.]

Re: Big Block oil consumption problem with pics

Joe, thanks for the thoughts. As you can see below the oil trail from the PCV is, I believe, minimal. Not enough for me to believe this is the source.

Would you or someone else be able to supply answers to these?

1. If these are teflon guide seals, were the bosses/guides machined?
2. If they were machined can I still install complete GM guide seals along with the umbrellas? If not, whats the best course of action?
3. Who produces a set of intake gaskets that would give the best chance of getting a good mating of the manifold/head? I've heard GM no longer has them available.
4. Is there another method of resolving this issue that I haven't considered?

I am open to suggestions. Back in the younger days I built many factory hi-perf rat motors and never had this issue. What the heck has changed???

[Clem Z.]

Re: Big Block oil consumption problem with pics

if the engine rebuilder used a spiral type guide liner you must use the positive type as there is a spiral groove from the top to the bottom of the guide which oil can be sucked into the port.

[G A.]

Re: Big Block oil consumption problem with pics

if the engine rebuilder used a spiral type guide liner you must use the positive type as there is a spiral groove from the top to the bottom of the guide which oil can be sucked into the port.

Clem, are you referring to a knurled guide?

[Clem Z.]

Re: Big Block oil consumption problem with pics

Clem, are you referring to a knurled guide?

no i was referring to a guide liner that "threads" into the guide BUT knurled guides would have the same problem as it would have a spiral groove also. knurled guides will only last a short time before the wear out and you have the same problem as before too much clearance in the guide. K line has a guide liner that has a "interupted" groove spiral type guide liner that keeps the oil from going down the groove

[G A.]

Re: Big Block oil consumption problem with pics

Well obviously I'm going to have to pull a spring to find out for sure. The rebuilders parts list shows new guides.

[Joe L.]

Re: Big Block oil consumption problem with pics

Joe, thanks for the thoughts. As you can see below the oil trail from the PCV is, I believe, minimal. Not enough for me to believe this is the source.

Would you or someone else be able to supply answers to these?

1. If these are teflon guide seals, were the bosses/guides machined?
2. If they were machined can I still install complete GM guide seals along with the umbrellas? If not, whats the best course of action?
3. Who produces a set of intake gaskets that would give the best chance of getting a good mating of the manifold/head? I've heard GM no longer has them available.
4. Is there another method of resolving this issue that I haven't considered?

I am open to suggestions. Back in the younger days I built many factory hi-perf rat motors and never had this issue. What the heck has changed???

Dan------


1) With the positive-type, all-teflon seals, the valve guide bosses usually must be machined to accept them. There are several sizes of these seals available but I don't think that any are sized to fit an unmachined boss. Besides, even if they were available, the OD of such seals would be too great to fit within most springs;

2) I don't think there would be a problem using the stock-type seals with the machined-down valve guide bosses. The stock seals should still function ok;

3) I prefer the original style embossed gaskets. These are GM-discontinued. One of the gasket companies probably still makes them, but I don't know which one. I've been unable to find them in the aftermarket. However, a simple solution to getting the original style gaskets is to buy the Paragon reproductions. They are the original style and are even correct with respect to other nuance features. However, rationally, any of the gasket sets currently available from the major gasket manufacturers should seal the ports unless there is some other problem. In that regard, do you know if the heads were surfaced and, if so, by how much?

4) If there is, I don't know what it is.

Definitely let us know how it turns out.

[G A.]

Re: Big Block oil consumption problem with pics

Joe,
Thanks for the info. I will certainly make a follow-up report. No, the heads were not shaved. All casting tolerances show on the receipt anyway, as original. That was one of the things I first checked.
Guess I have to lay out the course of action now.

Thanks everyone for the input!