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Scored Cylinders

Jim P

Well Known Member
Well, timing is not optimal. I scoped the cylinders after compression check today and found some vertical scoring in the cylinder walls on #1 and #3 with 600 hrs since new. Compression is 74/80 on both and oil consumption has been about 1qt/8-10 hours. I'm wondering about a bad ring that's moving around a bit. I have some carbon build up on pistons, any possibility it's just carbon getting caught by the wall? Thoughts?

And I've review this thread as well: http://www.vansairforce.com/community/showthread.php?t=112722&page=4

Here's #1: https://1drv.ms/u/s!Al5IppCB40wPg4BOajpH2AcctBEdAA
And #3: https://1drv.ms/u/s!Al5IppCB40wPg4BQe1D2Tm4HVc0bUA
 
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#1 certainly looks like either the ring developed a burr (likely at the gap) or has some metal debris embedded in it. You can see a distinct progression and stopping point. The scoring appears to follow the spot as the ring rotates. #3 looks very light from debris that cleared itself. More like scuffing than scoring and not much to be worried about here.

Not much you can do but pull #1 and bore it 010 or 020 over and re-ring. Haven't researched if it is possilbe to take only one cylinder 010 over. The larger piston likely exceeds the 14 gram weight tolerance for balance. However, it is possible they work the oversize pistons to meet the same weight as the STD pistons. There is certainly enough meat on them to make this feasible. These steps are probably not necessary until the oil consumption becomes intolerable or compression drops. This cylinder won't likely make it to TBO though without a lot more oil consumption.

Larry
 
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Oil consumption is ok. Compressions are ok. Any metal in the filter?

Like the other poster's mechanic suggested, I would continue to run it and monitor. FWIW.

Al
 
#3 doesn?t look bad, almost normal to have a few minor scratches like that, probably injested some dirt or grit and cleared itself. #1 however looks like classic scoring to me. Perhaps from a cold start or it may have happened during break-in. Is this the first scope on these cylinders? Can?t tell from the pic but that?s probably on the thrust side of the piston right? In any case, with a clean filter and with good leak down and oil consumption its a tough call, you could go either way (pull it or run it). I?ll take a guess there will be some minor aluminum particles in the oil filter, if so I?d pull that one cylinder.
Tim Andres
 
Forgot to mention, based upon the depth of scoring (the Pic seems to show some of scratches pretty deep, but tough to see) it is also possible that you have a broken compression ring. There are two of them in there and a leak down test (what aviation calls a compression test, which it really isn't) will often pass with one broken compression ring.

If this is the case, the wear and destruction will come much faster.

Larry
 
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Found that the area is smaller, probably about 5 degrees right at the 1200 position so it's not wrist pin. Pulled the filter and finger screen, both clean, not even any carbon flakes.
 
Found that the area is smaller, probably about 5 degrees right at the 1200 position so it's not wrist pin. Pulled the filter and finger screen, both clean, not even any carbon flakes.

Jim, One of my cylinders looks similar but less pronounced. There was no rusting before first run or flight. It has good oil control and had only 16 hrs when it was inspected. IO360M1B, new.

Is there any chance yours has set for over 30-60 days to get any rust in the cylinders? I am sure mine did not, so just checking.

My first filter was concerning, but the second was very clean. Do you get a regular oil analysis? That might help with a more refined monitoring tool.

BTW, as a career engine guy, it looks bad, but unless it has elevated metal, loss of compression (leak test), there is no overt indication that it is something that is progressing to failure. If it was a class 8 truck engine, it would not last, not sure about these Lycs.
 
Well crud! Bagged the trip to OSH to pull this cylinder - rather not be worrying about this over the Montana Rocks. Grrrrrr!
 
Good Call on OSH Canx

As a follow-up, we pulled the cylinder today and here's the result:
https://1drv.ms/u/s!Al5IppCB40wPg4BcDGa2Y8hNvcrvhg

The scoring on the cylinder looks like a broken ring, but all the rings were intact. One of the compression rings had some carbon build-up under the ring, so we thought that that carbon was actually pushing the ring outward and the gaps were scoring the cylinder. We'll see what the shop says. The actual scoring in the cylinder doesn't seem as bad as it looked and you can't catch a fingernail; the piston, however, is a different story.

Who knows how this would have progressed over the next 20+ hours, so it seems like the cautious approach and cancelling the OSH trip was a good call.
 
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