Ways to diagnose rings as source of oil consumption

[zwede]

Zwede, where is your PCV located and what style intake/throttle body do you use ?

It's a Holley 4150 style TB on a single plane (port injection) intake.

Also, the valves like that could indicate valve guide issues.

I thought so too which is why I had the heads refreshed. But all new guides/valves/seals did not change anything.

[zwede]

Since you have been using your bore scope could you also get a couple of pics of the actual cylinder walls on a couple of cylinders? If you have some major ring problem I think these pics will lead to that problem if it exists.

This is what I could find in my pic archive that shows walls.

Cylinder 2:

2_2.jpg

Cylinder 3:

3_2.jpg

[Belgian1979]

Zwede, where is your PCV located and what style intake/throttle body do you use ?

It's a Holley 4150 style TB on a single plane (port injection) intake.

Also, the valves like that could indicate valve guide issues.

I thought so too which is why I had the heads refreshed. But all new guides/valves/seals did not change anything.

I assume that on that 4150 style TB you have the pcv connected to the base. It would create an oil mist and that way it can end up on your butterflies. Have you tried to plug the pcv to see if it made any difference ?

[zwede]

1. I am guessing at this point that this is a standard 454 engine block and standard 454 stroke with a +.040 overbore? Kind of an odd overbore, why?

Yes, original block, crank, rods. It was already bored 030. I went 040 because that way I have at least one more bore if needed. Since it's #'s matching I want to stick with this block as long as possible.

2. Where the heads resurface cut anything more than .003" to .005" or more?

Just a cleanup pass.

3. Was the block decked any significant amount ?

Yes, big time. GM decked it crooked. Pass side deck was 020 high in the front, and driver's side 020 high in the rear. It is now decked to where pistons are 0.005" down.

4. Do you know what the rod and main clearances were set at?

All set towards the loose side of GM spec. I think rods at 0.003"?

5. Was there any change in stroke?, Rod length?

No

6. With the engine running have you pulled the PCV hose and PCV and looked for how much pressure is coming from the crankcase. Simple quick check done at idle and maybe 2500 rpms?

Tried it some time back. Didn't notice much. I have a breather on the pass valve cover and it doesn't spit oil at WOT even though that valve cover has no baffle (the cover with the PCV valve is baffled).

7. Why such heavy oils on what at this point seems to be a pretty mild street engine?

Heh, the machinist told me to run 20W-50! I settled on a 40 weight as I'm in a hot climate and don't drive it when it's cold. And yes, it's is definitely a mild street engine.

[zwede]

I assume that on that 4150 style TB you have the pcv connected to the base. It would create an oil mist and that way it can end up on your butterflies. Have you tried to plug the pcv to see if it made any difference ?

Yep. Tried disconnecting PCV and nothing changed. That was a head scratcher. I was so sure my oil problem was PCV.

[Belgian1979]

That would only leave the head studs. I also used blue silicone to seal them. I also got comments these could start leaking.

[Newold1]

OK, thanks for the replies and pics!

First, couple of things:
1. Those cylinder walls in the pics have way to much vertical scratching/scuffing from either a lot of hard carbon coming of the piston tops.
remember the oil control of the rings is supposed to clean the oil off the walls to a point. All those vertical scratches hold oil and the second ring and oil ring are supposed to scrape off most of the wall but they ride on the high points of the wall not into the scratches so all that oil remains on the wall and can work its way into the chamber and burn.
2. Your clearances at .003" w/possible plus are pretty loose for a mild stock build and with your pretty high oil pressure can sling a lot of oil of the rods and crankshaft and add to overcoming the oil control of the rings. I would have recommended clearances of about .002" on the rods and maybe .025" on the mains and I would like to see your stock oil pressure at about 50-60psi at lets say 5000rpms.
3. Are your intake gaskets the type with the metal insert blocking the internal exhaust heat riser in the intake to intake manifold connection. The .020" cut off the top of the block is a LOT and depending on what the original deck height actually was you could have a sealing problem and leak under vacuum at the bottom of the intake ports even if new gaskets were installed, especially with the Edelbrock intake if it was ever cut before or is out of square slightly.

I see a few strong possibilities here and all three in combination could all contribute to your oil consumption problem. JMO

[statsystems]

From the picture of the number three cylinder I can't tell if there is pitting from moisture on bore, or it we are seeing the cutter marks from the boring bar. It looks like tooling marks to me.

If you don't hone past the tooling marks from the boring bar, you can put any finish on the cylinder walls you want and it will be an oil burner.

A dull tool, improper feed and/or speed will require MORE stock left to hone to get past tooling marks.

I've used boring bars for production where you have to run the bar wide open and slam the tool down the hole to make "time". To get the tooling marks out I had to leave .006 so it would clean up. Instead of letting me slow the machine down a bit and doing I correctly, I spent whatever time I saved at the boring bar at the hone.

Just something to look at.

[Belgian1979]

What I still don't understand with a ring seal problem : how do you get oil in the intake and how come it doesn't show blue smoke in the exhaust ? If it uses that much I would at least assume it would show.

[Belgian1979]

What I still don't understand with a ring seal problem : how do you get oil in the intake and how come it doesn't show blue smoke in the exhaust ? If it uses that much I would at least assume it would show.

[zwede]

Thanks for the responses.

The oil pump is a STD volume melling w/ the Corvette spring so that's why it makes a bit more pressure at rpm.

I know the wall finish was perfect at time of assembly so anything you see in the pics must have happened afterwards.

I never ran the metal inserts on the intake gaskets as my intake has that area blocked off.

The intake was machined at the same time and seems to fit well. I tested it by torquing down with a cheap white paper gasket and then checked the impression. There is also the proper gap to the china wall (although I use RTV instead of end gaskets there).

So if the walls were scratched by carbon, is it something that will improve with time or is a re-hone & new rings the only fix?

[zwede]

What I still don't understand with a ring seal problem : how do you get oil in the intake and how come it doesn't show blue smoke in the exhaust ? If it uses that much I would at least assume it would show.

Overlap will push it into the intake. Don't know if you remember the LT4 Corvettes of the 90's but the cam had enough reversion that it added so much exhaust into the intake at low loads it passed emissions without EGR.

As for the lack of smoke, I think it's because the oil leaks constantly so it's a small enough amount to not smoke, but since it leaks all the time it adds up to high consumption.

[Belgian1979]

Well, if you're convinced it's ring seal, there's only one option and that is to take it apart, rehone and new rings. Keep us informed.

[zwede]

Well, if you're convinced it's ring seal, there's only one option and that is to take it apart, rehone and new rings. Keep us informed.

No, I'm not convinced about anything. Sorry if I gave you that impression. That's why I posted this and want to discuss. The last thing I want it to be is rings because that's the most work to fix. It's just that I think I'm out of other things it can be, so I posted here for opinions and others experience. I hope it turns out not to be rings.

[Newold1]

Well I am at a point in my analysis that I think this is a "ring oil control problem" not a ring seal compression issue. IE the decent compression measurements and low leak down numbers. I would say after all the good answers to all the questions that things are not right in those rings, and cylinder bores. It looks to me if you want to cut the consumption down to some decent ranges you are going to have to take that baby down.

Just be careful because re-honing or whatever has to be done to correct the bores and finishes is going to open the clearances even farther and a rocking forged piston in a mild build is gonna rattle a bit and have other possible issues. Use a really good set of Total Seal AP moly ring set and do theTotal Seal recommended final bore finish.
I would also recommend a new set of bearings with plus sizes to tighten up those rod and mains clearances and be careful to measure the rods side clearances and keep them from being to big where the oil slinging will be an issue.

Take that high pressure spring out of the pump and try for 50-60psi oil pressure.

Use a good break in oil with a good wear package and switch to a 10-30 synthetic when done. You don't need that heavy oil.
JMO