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Re ringing old cylinders

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OK, I have a question for you aviation gear heads. I've been a mechanic for 55 years on cars and have done this process on them.
My hangered RV-6A I bought flying 180 hours ago has a question.
My 460 hour channel chrome cylinder 8.5-1 comp 0-360 with SDS ignition and fuel injection. Burning a quart in 5 hours of Areo Shell 20x50.
Operated at 2200 RPM and 26" @ MFP 4500 feet on Costco premium fuel
Compressions are good and borescope shows very minimal vertical scratching in cylinders. No crosshatching as is normal in Channel chrome cylinders.
Run the motor an hour, pull plugs, look in cylinders and see slight oil puddling in bottom.
Just for the giggles I ran it for 40 hours using Phillips 15x40 mineral oil and no difference.
Oil changes with Blackstone analysis every 30 hours, All good, But oil gets pretty dark after 4-6 hours.
I did the Mike Busch fluid flush, 1,3,4,all flushed expectably, But #2 wouldn't flush at all first time, Ran for 6 hours and then it would flush at about 30 percent.

::So on to my question::
Does anybody have any idea as to just pulling cylinders and installing new rings to see it that will help with oil consumption and blowby. I understand you can't rehone channel chrome.
I have an Anti-splat oil separator installed and belly is relatively clean.

Not a big job or very expensive the way I see it if it would help. Rings, through bolts/nuts, gaskets and seals,
Seems like it might be worth a try.
Anybody thinks it might be worth a try?????
Thanks Art
 
I have channel chrome cylinders and see the same exact thing you do. Oil in cylinders, 5-8 hrs per qt, gets dirty quickly, etc. I've got about 650hrs on mine.

From what I read, sometimes removing cylinders just creates new problems. I would opt to just leave it. Oil is cheap!
 
It's fine, leave it be.
Your oil consumption rate is far less than what Lycoming considers bad.

If you don't re-hone the cylinders... how will the new rings ever seat?
So you'd be looking a overhauling all 4 cylinders, not just new rings. Around $3600. Buys a lot of oil.
 
You can make it worse if you don't do it right.

If you decide to tear it down, make sure you have a set of torque plates on hand. Only do 1 cylinder at a time. Read Mike Busch's Why I Hate Pulling Jugs article first.

EAA_2015-07_why-i-hate-pulling-jugs.pdf


EAA_2014-06_cylinder-work-be-afraid.pdf
 
Mike is talking Contenental. Not all engine shops agree with Mike on this.

Bingo! I agree with Mike on far more than a majority of things, but pulling a Lycoming jug is in the manuals and considered standard for these engines. And yes - Lycoming says you need to use torque plates when a jug is off.

Paul
 
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I am guessing you have glazed cylinders. I have had the same problem with a Lyc 320.
I had the cylinders honed, installed new rings, towed it to the runway and ran it hard for a break in.
Oil usage went down to regular usage and the engine ran great for several hundred hours till it was sold.
Channel Chrome cylinders are harder to break in than the normal steel or cermichrome cylinders so you have to be careful not to glaze them.
I know they say it won’t work, but It worked for me and was a cheap fix.
YMMV
 
I am guessing you have glazed cylinders. I have had the same problem with a Lyc 320.
I had the cylinders honed, installed new rings, towed it to the runway and ran it hard for a break in.
Oil usage went down to regular usage and the engine ran great for several hundred hours till it was sold.
Channel Chrome cylinders are harder to break in than the normal steel or cermichrome cylinders so you have to be careful not to glaze them.
I know they say it won’t work, but It worked for me and was a cheap fix.
YMMV

Steve, you honed chrome cylinders? I thought that was not recommended. If the "blue paint" cylinders are glazed, then it seems honing and replacing the rings is a good fix. I guess with chrome, you can only change the rings, if the oil burn rate is bothering you.

@Art - you said that all flushed well except #2 - do the other cylinders also pool oil? Did your consumption drop after the flush?
 
“Steve, you honed chrome cylinders?”

Yes. Using the brush type hone. A local auto rebuild shop did it for me.
 
I don't believe that chrome cylinder should be honed in the traditional manner. If they are glazed, you can use a maroon scotch pad to break the glaze and allow new rings to seat. Could possibly use a 400 grit ball hone as well (just enough to remove the glazing. I would NOT run traditional 220 grit honing stones through a chrome cylinder. If they are glazed, simply installing new rings will not solve the oil consumption problem. If they are not glazed, I would seek the expertise of a cyl overhaul shop, as more than honing may be required to improve oil consumption issues.

I also have no issues with removing Lyc barrels, if proper precautions are taken.

Larry
 
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The rings might have been installed upside down. When using certain rings on chrome cylinders, the dot on the ring goes down, not up, as it would in plain steel or nitrided cylinders. This is specifically for oil control due to the slick surface of the chrome. This is one of those footnotes in the overhaul manual that is easily missed. You would benefit from breaking the glaze on the walls, and installing new rings, and then a 3-5 hour break in period.
 
Observations - no recommendation.

--Burning a quart in 5 hours of Aero Shell 20x50.
-- minimal vertical scratching in cylinders.
-- Oil changes with Blackstone analysis every 30 hours, All good, But oil gets pretty dark after 4-6 hours.

These are the key attention getters to me for different reasons.

5 hrs/qt - -assuming you are already operating at 6qts or less - not ideal but not specifically actionable.

vertical scratching+black oil in 4-6 hrs seems unusual - -bringing the oil analysis to the equation - could you post a couple of the oil analyses to see what is happening there? May help-may not.

Piston-ring-liner tribology is a dark art to some degree at least that is my sense of it from swimming in the engine development pond- I'll leave that to true experts (Mahlon ?). Chrome walls-rings have some specific behaviors, namely scuffing which is why the channels are in there for lubrication to prevent hot spots that would result in smearing of the chrome. That is a reality for chrome, but have no idea if it relates to your situation. If-if-if it is present, I could see why the ring/barrels could need replacement. The parts forward at this point sounds like a personal preference or call trusted an engine expert with these specific parts. Trust a person, then their answer - - not me:eek:

Final thought after previewing - a high resolution photo of the walls might reveal material transfers to/from the walls. It could lead to a more definitive evaluation for an expert.

Sidebar story - I remember early in my engine life a story about chrome rings in a 5.4" bore CAT diesels. An engine using the same valve, bore-stroke as the Merlin. A high performance V12-v16. The story goes, that field issues of oil consumption was solved many times with a can of BonAmi, used to dust the engine while running under load. They swore it solved the problem and the engine ran happily ever after. The chrome rings were compression and scrapers. Chrome plating on oil control rings persisted for several decades. I guess the contact pressures (of oil rings) don't push it's limits. Not something I would do, though, scary. Plasma faced rings replaced chrome in mid 70's for diesel.

I do know for a fact it only takes a tiny fraction of open areas of non contact of an oil ring to yield a noticeable increase in oil consumption.
 
My thanks for the insight.
Post 3-- I was thinking of just pulling cylinders. lite hone, new rings, reinstall. Not OH cylinders.
Post 4-6-- I agree with the thoughts on torque plates even though I don't really agree, But I'm not an airplane wrench.
Post 7-- I don't see any glazing, just bright shiny turtle cracked cylinders with no pieces missing. Did you do what I'm suggesting? Just pull, hone, clean pistons, and reassemble with new rings?
Post 8-- Yes there is oil pooling in all cylinders, Flush did nothing to change consumption. Actually #4 plug looks the oiliest. Plugs are brownish not tanish like they are supposed to be.
Post 9-- Yes 26" at 2200 CS prop in cruise. Runs good. Like running your car in top gear. I do not believe in the "have to be squared" theory. I had a Cessna 206 with an IO-520. Did the same thing with it. Never BLEW up. Obviously take off was full fuel and fine prop.
Post 11-- This is the one I was pondering the most. I wasn't sure you could hone the channel chrome cylinders.
Post 12-- I'm sure if it contacted a "professional" OH shop they would recommend sending them in for OH and NOT recommend a DIY home fix. That is their job. I'm also sure they would never recommend the patch work I'm talking about. And would laugh in my face.
Post 13-- When changing oil and filter. I fill with 6.5 quarts puts it at 6 qt mark, burn till 4.5 and add a quart to 5.5. I have analysis at hanger and will get in two days, I only have one picture of a cylinder at home.
The kicker is I'm not broke and can afford new engines, But I like to fix things if I can.
The question is has anybody ever done this? It seems like it should be able to be done. But, them chrome turtle shell cylinders is the reason for this thread.
Anybody else have any thoughts?
Thanks again Art
 

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(The following is all book knowledge, and this being the internet I wouldn't trust me....its just a couple of ideas, which is what you requested)

I think the general recommendation for engine Break In is "run it hard."

Did you break it in at 2200 rpm and 26" mp? Do you think you were running it hard enough to get a good break in? It looks to me like thats about 130hp, or 72% power, which to me that seems like its on very low side of prudent.

At this juncture in time, I'll believe I'll break my engine in harder than that if the temps all stay agreeable. I want lots of pressure on those cylinder wall/ring interface to scrape off the microscopic "mountain tops" of the fresh hone before oil gets cooked/baked into the microscopic "valleys" and clogs/glazes them up.

Second. It seems to me like you like to fix things. What is the risk if you do the fix IAW the Lycoming overhaul or service manual and all the service bulletins, along with coordinating your work (for pay) with a good mechanic? Seem like its a win-win.

I like Mike Bush. Follow Lycoming's instructions and understand what the risk is that Mike is concerned about and I think you'll be able to navigate it. (Use cylinder hold downs, and dont spin a bearing.....I think that would be Mikes concern.)

I like Mike because he has data...and that data can be used to create Fear Uncertainty and Doubt, so I listen and feel safer and educated. Plus I don't really understand what the risk mitigation strategy is. But folks do overcome the risk everyday. Education and understanding is really how we make a dangerous hobby into a safe hobby. So then I go find out what errors are that cause the failures and learn that there is a way around the risk after all....making a dangerous thing like cylinder removal into a prudent and safe activity.)
 
As far a breaking the engine in. Have no clue as I said I bought the plane flying a 180 hours ago and it has always burned oil.
Yes, I have read most of Mikes info on the bearings having to be retained, My comment on the case clamping was because I have had enough engines apart to see the quite large bend out on the mains.
I'm in an experimental world here, so why not experiment. Now I don't mean to be dangerous here, Fly the &#6 out of it after the work for sure to get a good break-in.
I've just never heard of it being done.
More also of an education to others as to not wanting to ask the question as to what, where, how, and CAN it be done?
I added a few pictures
The scratching is mostly on the tops of the cylinders like cold start high rev syndrome, Nothing at the pin regain.
Thanks Again Art
 

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Those are some crazy looking cylinder walls. I hope someone has an idea what that is. FWIW I have some overhauled cylinders that were chromed on my engine (orange stripe). The bore scope pictures definitely DO NOT look like yours.

Savvy (Mike Busch) has a paid Q&A service. I bet they know what to make of that crazy pattern.
 
Channel Chrome

The crazy pattern is Channel Chrome. It is what channel chrome looks like.
It looks Weird cause it is and doesn't work very well, Because it is hard to get a good break in on the rings.
Most people have oil burn problems with these.
Not done anymore as far as I know.
I've decided to just burn oil as I have a number of cases under the bench. Oil is cheap if you have an excess. Just have to watch it.
If it get worst, Well, then maybe I'll pull it down next winter and re-ring only.
I just bore-scoped the engine yesterday and all the valves look perfect.
The old comment is " Wish I didn't have them, But, gotta live with it for now"
Thanks for all the info Art
 
The crazy pattern is Channel Chrome. It is what channel chrome looks like.
It looks Weird cause it is and doesn't work very well, Because it is hard to get a good break in on the rings.
Most people have oil burn problems with these.
Not done anymore as far as I know.
I've decided to just burn oil as I have a number of cases under the bench. Oil is cheap if you have an excess. Just have to watch it.
If it get worst, Well, then maybe I'll pull it down next winter and re-ring only.
I just bore-scoped the engine yesterday and all the valves look perfect.
The old comment is " Wish I didn't have them, But, gotta live with it for now"
Thanks for all the info Art

Possibility that you have too many cracks in the chrome, where the oil resides and then gets burnt during the combustion process.

https://southernairboat.com/communi...ld-and-recondition-first-tbo-to-chrome.71806/
The chrome job is not a sleeve. The cylinders are turned oversize and the chrome is applied directly to the steel. It's called "Channel Chrome" and seems to be as much art vs. science to get a good result. When properly done, the chrome looks like spider cracks in tempered glass (before it all falls apart). The cracks hold the engine oil to lubricate the rings. Too large or too many cracks and the motor burns oil like fuel. Not enough and the rings do not get proper lubrication.

Chrome is hard and can't be machined like steel. It might be possible to ground down the chrome, not sure on that one? :dontknow:

As Gary says, the chrome does not wear as fast, the rings do. Steel cylinders get chrome rings. Chrome cylinders get steel rings. It's a lot easier/cheaper to replace rings as long as the cylinders remain in spec.

Put a lot of pitch in the prop and run it hard through multiple heat cycles as Gary says. I have chrome cylinders with about 25 hours on them since overhaul (took a year to get them done). They used a lot of oil for about the first 10 hours and then stabilized at a quart every other tank. Been running the **** out of them since overhaul./B]
 
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