Cracked Cylinder or ?

[tim417]

While prepping my 63 C model for annual this week, I scoped the cylinders and found this in cylinder 3 next to the exhaust valve. My A&P and I suspect a crack and I am prepared to replace the jug, but my Savvy Aviation IA suggested it would be worthwhile to clean it and examine whether or not it is simply a crack in the deposits. Worst case, I pay for a little labor and have to trash the jug. 

What do you guys think? Cracked?

 

[201Steve]

Sure looks like it, but the only way to know for sure would be to yank the jug I would think. Unless you are able to ascertain 1,000% that it’s NOT a crack, sure would be thinking about it a lot during flight. I guess it’s theoretically possible to get some dye penetrant in there with some funky angled spray tips and tools. Nice find!

 

-Not an A&P, very minimal cracked metal experience. 
 

[markgrue]

Not cracked.   I agree with the IA.  Just the deposits.

 

Mark 

[gwav8or]

I'm not an A/P but I agree with Savvy, that looks like cracks in the deposits.  I'd have your mechanic clean it properly and thoroughly (per Savvy instructions/advice) and see where it's at after.  

[A64Pilot]

I’m betting it’s a crack, I don’t see any carbon build up, I see carbon build up beside the suspect area though.

I’d be more interested to know if that crack even really matters though

Edited April 29 by A64Pilot

[Old Chub]

I feel it is a crack in the deposits.  The third photo seems to show a buildup around the valve area.   The hoop stresses in the valve area usually produce a crack emanating from the valve seat bore.  That would be extreamly rare type of crack next to the valve seat. 

[DXB]

I imagine cleaning this deposit area off without pulling the jug should be feasible with the right tools?

[N201MKTurbo]

Scrape the deposits off by putting the borescope through one spark plug hole and your scraper through the other spark plug hole. Making the scraper will be interesting. You could heat a screwdriver and bend it just right. if you can make an effective scraper, it will take about 4 hands to do it.

[varlajo]

9 minutes ago, N201MKTurbo said:

You could heat a screwdriver and bend it just right.

I use dental tools for that

[Nico1]

Please post the after scraping photos, will be interesting to see! (And of the process too if possible!)

[Jim F]

I have lots of borescope experience.  I don't see the valve seat transition, that tells me that there are deposits built up.  It's a little bit of an odd place for a crack, but don't put too much in that statement.  I would fly your AC at a high-power setting and take another look.  Also, before i would pull the jug I would drop the exhaust and look at the port position side of the potential crack position. 

Jim

[N201MKTurbo]

11 minutes ago, varlajo said:

I use dental tools for that

If you have all of them at work, that would work....

Do you have one that will go in a sparkplug hole bend around where you need it? It doesn't seem like an angle you would need in a mouth.

[EricJ]

Most likely just deposits.    Like most things with cylinders, I'd just run it a while and check it again later.   

[tim417]

Thanks for all the feedback. I’ll definitely keep everyone posted as to what we find!