Cylinder Deposits

[Dbarbee]

I took my first peak inside my cylinders today since the engine was installed and was a little surprised at what I saw. I was expecting to see shiny smooth cylinder walls with lots of crosshatch remaining but instead saw what appeared to be splotchy white deposits. The pictures aren’t great but I’m hoping someone can give me an idea what I’m seeing. I didn’t notice the orange tint that shows up in the picture so I don’t know if that’s real or just from the low quality picture. I’m mainly wondering about the white splotchy deposits at the upper end of the cylinders.

A little background...

I bought the engine from Wentworth with 17 SMOH and took it to a local engine shop for a full tear down inspection. New Lycoming cylinders were installed at the overhaul and they were re-honed during the inspection and new rings were installed.

I’ve flown it at 75% power for the last 60 hours since the inspection with Phillips 20W/50 mineral oil. First oil & filter change at 10 hours and the next two at 25 hour intervals.

Compression on all four cylinders is 79/80

Oil consumption seems to be leveling off around 10 hrs/Qt

Spark plugs were clean and dry

Should I be concerned or is this normal to see in a freshly overhauled engine?

 

[mwagg737]

What engine?

 

[Dbarbee]

What engine?

Yeah, I guess that would be important information

Lycoming O-360-A1F6D

 

[William Pete Hodges]

I am no expert but it looks like lead ash to me. Why do I say that? Back in the 60s and 70s all auto engines burned leaded gasoline and it left a chalky white-ish powder on the inside of the entire exhaust system. So if you were looking at a used car and wanted to know if it was burning oil, you took your finger and wiped out the inside of the tail pipe. If it was greasy or black that was bad, but if it chalky and white or light tan that was good. In your pictures the gray is at the top of the cylinder around the cumbustion chamber. 100LL has a lot of lead compared to leaded regular mogas, so I wouldn't be surprised to find lead ash up there.

Does your engine use too much oil or have low compression? Not likely with only 77 hours. I think you are ok.

 

[mwagg737]

What kind of cylinder head temperatures do you see?

 

[GRG55]

I would suspect lead deposits.
You should check with "the competent authorities", but I believe you should be breaking in the cylinders at full power, not 75%.

 

[Aviator305]

I would suspect lead deposits.
You should check with "the competent authorities", but I believe you should be breaking in the cylinders at full power, not 75%.

No, he is not supposed to be cruising at full power for break in.

 

[Dbarbee]

I am no expert but it looks like lead ash to me...Does your engine use too much oil or have low compression?

Lead sounds like a reasonable explanation. I don’t know why that didn’t occur to me before, guess I’m just used to seeing it on the plugs and not the cylinder walls.

As I mentioned before, oil consumption has been steadily dropping off with only 2 qts added in the last 25 hours and all cylinders are at 79/80 compression.

 

[Dbarbee]

What kind of cylinder head temperatures do you see?

CHT’S at first were all just above 400 in cruise but are starting to work down into the mid to high 390’s. Even the original engine was difficult to get much lower than 390 at 75%. (My baffle seals need some work)

 

[Dbarbee]

I would suspect lead deposits.
You should check with "the competent authorities", but I believe you should be breaking in the cylinders at full power, not 75%.

The Lycoming oil consumption and break in manual says to cruise at 65%-75% power until oil consumption stabilizes.