The International Cessna^® 170 Association

Curious what you all would do to troubleshoot the following.
I sent a sample (report attached) when I took the airplane down for annual last week.

Overall it has been running fine; on one flight late last year there was just a hint of rough running on a night takeoff, barely noticeable but just a hint of roughness. I flew for 90 minutes or so before the annual / oil sample and it ran fine.

We are planning to borescope the cylinders during the inspection.

Thanks in advance.

Tom, while you are Borescoping your cylinders also look to see if a piston pin end plug has been scuffing the cylinder wall.

The borescope images were not super conclusive; #4 appeared to have a slightly different pattern on the cylinder wall but nothing that looked like a pin scuffing or anything else.
I will see if I can post images later.

Our current plan is to fly it 5 or so hours and send another sample.

Any other thoughts?

Is five hours enough to get a good signal in the next analysis? I'd probably shoot for ten.

Good point; that is what my A&P wanted to do.
He is a reasonable guy so I will d/w him.

Thanks

I’m curious why the lab thinks “break-in” occurred in 2021. Has there been a cylinder change?

Have you made a change in oil type/brand during this history? Do you use any additives? (noticing calcium, magnesium, phosphorus)