Big Block oil consumption problem with pics

[Robert G.]

Re: Big Block oil consumption problem with pics

I'm no engine expert, but I've never heard of compression numbers that high. Whether that has anything to do with your problem, I'll leave that to the experts.

[Joe L.]

Re: Big Block oil consumption problem with pics

I'm no engine expert, but I've never heard of compression numbers that high. Whether that has anything to do with your problem, I'll leave that to the experts.

Robert------



You're right; I missed that. If the first digits were a "1" rather than a "2", it would be about right.

[Domenic T.]

Re: Big Block oil consumption problem with pics

Robert------



You're right; I missed that. If the first digits were a "1" rather than a "2", it would be about right.

Joe,
Sounds like he has cold oil in the cylinders to get high #'s like that.
Do you remember that old procedure used when checking for bad rings? The one where oil was squirted in the cylinder and the compression recorded then washed out with gas and recorded?
The compression was way up there on good rings because the oil sealed the end gaps.
Ive seen the readings over 200 but not that high unless he has a gapless ring set.
DOM

[Ted S.]

Re: Big Block oil consumption problem with pics

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.

I'm with Joe, What type of intake gaskets were used? Any sealant used around the intake ports? They can be a real bear to get to seal especially once the heads have been surfaced or the block decked.

[Ted S.]

Re: Big Block oil consumption problem with pics

Victor Reinz carries the embossed gaskets. They carry two different ones for rectangle port heads. One of them is like the print-0-seals but the "stock" one is embossed like the originals. I know Carquest carries them.

[Edward J.]

Re: Big Block oil consumption problem with pics

DAN, When I look at the photos,To me its has clear signs of oil running down the guides, the dark traces of black on the valve is burn oil , and theres is surely alot of deposits on the valve to indicate oil usage.and in one of the photos there appears to be a drop of oil on the end of the guide. Replacement of the seals would surely be the easiest thing to perform. There surely must be a reason of the early failure of these seals or possiably the wrong dia. another thought would be did the machinist cut the top of the guides enough? so if the lifters did pump up to much at high RPMS(5500/6500) The retainer can come down at hit the tops of the seals and destory them. removel of one of the seals to inspect would show any damage.

[Ken A.]

Re: Big Block oil consumption problem with pics

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

Those are perfect circle seals and they're good. Chevy also made a valve spring retainer with a built in seal that worked very well due to the high oil pressure "wash over". Also big blocks were notorious for blowing out the first quart of oil, probably due to the PVC system, as Joe says. We always ran the engine 1 qt. low and never had a problem with starvation. And after losing the first qt, I'd bet your problem goes away.

[G A.]

Re: Big Block oil consumption problem with pics

Based on the confidence I had in the overhauler, today I removed the intake under the assumption that it had to be a leaking gasket, thanks to the many that suggested that. In fact I did find most of the runners in the head wet with oil :-).
As I took a flashlight to further inspect the guides/valves I found this. What strikes me is that some guides are smooth and appear new, while others look rough, like they've been through a vat. It appears to me that some guides were replaced and others not. What do you guys think? If so, I'm going to remove the heads to have them massaged. These are all from the left bank. The guides in the right side all appear new, smooth not rough.

[Jim M.]

Re: Big Block oil consumption problem with pics

Dan: My two cents worth, from personal experience, is that GM could have used "positive" type valve stem seals on the big blocks, but the engineers decided instead to use the "umbrella" seals. Neither expensive nor difficult to make the change and see how it works. Thanks Jim

[Clem Z.]

Re: Big Block oil consumption problem with pics

Those are perfect circle seals and they're good. Chevy also made a valve spring retainer with a built in seal that worked very well due to the high oil pressure "wash over". Also big blocks were notorious for blowing out the first quart of oil, probably due to the PVC system, as Joe says. We always ran the engine 1 qt. low and never had a problem with starvation. And after losing the first qt, I'd bet your problem goes away.

with my BB corvettes i had to run a quart over because when i got to the end of the 1/4 mile drag strip the oil pressure was dropping because the oil was not returning fast enough to the pan. even now days chevy tells you in the owners manual to run a quart over full if using your corvette for autocrossing or track days as they still have the same problem the oil stays upstairs. i have found if you do not have the correct PCV valve for your engine you will burn oil. i know of one guy who overhauled his engine and it still burned oil but putting in the correct PCV valve stop the oil burning

[Joe L.]

Re: Big Block oil consumption problem with pics

Based on the confidence I had in the overhauler, today I removed the intake under the assumption that it had to be a leaking gasket, thanks to the many that suggested that. In fact I did find most of the runners in the head wet with oil :-).
As I took a flashlight to further inspect the guides/valves I found this. What strikes me is that some guides are smooth and appear new, while others look rough, like they've been through a vat. It appears to me that some guides were replaced and others not. What do you guys think? If so, I'm going to remove the heads to have them massaged. These are all from the left bank. The guides in the right side all appear new, smooth not rough.

Dan------

Do you know if they installed thin wall guides? A thin wall guide is installed within the existing guide, so what you would see in the ports is the bottom portion of the original guide, not the new guide. Personally, I don't like thin wall guides, but they have been used effectively for many years.

It may also be that some of the guides were not worn, so no replacement was necessary. Sometimes, the wear is mostly on the valve stems, so the problem is cured when the valves are replaced. Some of the guides may have been worn and, perhaps, they replaced those with thickwall guides.

[G A.]

Re: Big Block oil consumption problem with pics

Thanks Joe,

I forgot about thin wall guides.
The rebuilder didn't log those kinds of details and says they can't recall. I'll still have to remove a spring to see. I am very tempted to pull the heads and have them built back to specs. I think I would rather spend some money and know what I have rather than try to resolve one problem only to then discover something else, like a worn valve.

Is there a machine shop in Houston that you or another member might recommend?

[Clem Z.]

Re: Big Block oil consumption problem with pics

Dan------

Do you know if they installed thin wall guides? A thin wall guide is installed within the existing guide, so what you would see in the ports is the bottom portion of the original guide, not the new guide. Personally, I don't like thin wall guides, but they have been used effectively for many years.

It may also be that some of the guides were not worn, so no replacement was necessary. Sometimes, the wear is mostly on the valve stems, so the problem is cured when the valves are replaced. Some of the guides may have been worn and, perhaps, they replaced those with thickwall guides.

the valve guides in a BBC were bored after installed in the heads and sometime the bore was not concentric with the outside dia. this is one reason you have to use guide liners in the original guides to keep the valve on the same center line as original or you will have a problem with the valve seat and the valve being way off center. don't as me how i know this.

[Dick W.]

Re: Big Block oil consumption problem with pics

Another source of oil comsumption often overlooked is exhaust valve guides. Quite a bit of oil can pass by them

[Domenic T.]

Re: Big Block oil consumption problem with pics

Dan,
I got in on this at the tail end and didn't read all the replys but as long as you have that compression I would measure the guide clearance. I can feel them and tell, but if they are not to loose it's got to be the seals, (especially intake).
I have smashed a few seals myself while assembling with a pneumatic valve compressor and had to stop and put a new ones in.
Some spring designs are not good for some seal designs.
If guides are good and the boss will take the right seals you can do it all from the top. Maybe you will have to take a close look at the springs too.

DOM