How Do You Like These Jugs?

[RoundTwo]

Today I did a routine borescope inspection and found some strange marks on the walls of #1 cylinder. In general, there are three concentric rings of short “scratches” running around the circumference of the cylinder. They’re coplanar with the face if the piston and appear to be about equally spaced. The pattern runs pretty much, if not totally, around the circumference. Each scratch appears to be about 1/4 to 3/8” and they appear to be in “groups”, like something was skipping around the circumference. I can’t guarantee they were there the last time I scoped the jug. 

The compression is fine and the engine is running like a top. Without any external input, my plan is to continue to run it and scope more frequently to see if things change. Thoughts?

IO-360 1,600 TT 500 TSTOH Jugs are ECI Cerminil, installed about 12 years ago.

[takair]

I wonder if it isn’t simply the way someone honed it?

[PT20J]

Kind of strange. I would call ECI and ask their opinion. How deep are the scratches? It's hard to tell from the pictures, but if they aren't deeper than the cross hatch then Lycoming told me that scratches are not an issue. Another test is to see if they catch a dental pick run across them.

But, if it is running fine and not using oil and oil analysis is good and the filter is clear of metal, I personally wouldn't be too concerned about it. 

Skip

[Eight8Victor]

Get in touch with Zephyr, They are always accommodating and willing to help. It would be interesting to know their thoughts on what created these marks. 
 

How often do you fly? Has the engine been idle for long periods of time? Do any of the other cylinders have marks?

 

Edited November 28, 2023 by Eight8Victor

[RoundTwo]

9 hours ago, PT20J said:

Kind of strange. I would call ECI and ask their opinion. How deep are the scratches? It's hard to tell from the pictures, but if they aren't deeper than the cross hatch then Lycoming told me that scratches are not an issue. Another test is to see if they catch a dental pick run across them.

But, if it is running fine and not using oil and oil analysis is good and the filter is clear of metal, I personally wouldn't be too concerned about it. 

Skip

Great idea to call them. No idea on severity of scratches because jug is still mounted. 

[RoundTwo]

1 hour ago, Eight8Victor said:

Get in touch with Zephyr, They are always accommodating and willing to help. It would be interesting to know their thoughts on what created these marks. 
 

How often do you fly? Has the engine been idle for long periods of time? Do any of the other cylinders have marks?

 

I’ll give Zephyr a call today and see if they have any insight. The engine gets plenty of use, 120+ hours since April and these marks are only found in #1. 

[Utah20Gflyer]

I can’t come up with anything that would do that while the engine is running which makes me think these scratches were created prior to being mounted, ie during manufacture.   Given that they function properly I see this investigation as a geewhiz activity.  It would be interesting to find the answer but it really doesn’t seem to matter in any practical sense.  

[PT20J]

3 hours ago, RoundTwo said:

Great idea to call them. No idea on severity of scratches because jug is still mounted. 

You can run the pick through one spark plug hole while observing through the other.

[EricJ]

6 hours ago, RoundTwo said:

I’ll give Zephyr a call today and see if they have any insight. The engine gets plenty of use, 120+ hours since April and these marks are only found in #1. 

If compression and oil use are okay and it's running well it may be good to just keep running it and keep an eye on it to see if it gets worse or not.

 

[RoundTwo]

General consensus is that the scratches were in the jugs before installation. As everyone has stated, there’s no easy way to explain how they would happen in a running engine. To prevent turning this into an academic research project, the plan is to fly normally and check it again at the next oil change. I have to assume that nothing will be changing.