Boroscopes and Cylinder Heads

[jonweisw]

All - I am in the midst of an annual on my 460h IO-360M1B on my RV-8, and, having never done this before, I decided to boroscope the cylinders. I was surprised to find that the cylinder heads had large patches of multicolored irregularities - some cylinders worse than others - almost like flat patches of material. I dont think that it represents rust as I fly pretty regularly, but I was surprised by the amount of it (unfortunately I couldnt get a picture with this particular scope). The cylinder walls looked good as did the rings.

Does anyone know what this is? I run my engine with aggressive leaning to keep it about 50deg rich of the hottest cylinder and the cht's all run within about 10-20deg of each other. Compressions are all very good (76-80).

Anybody with some grey hair on this subject have any thoughts?

Jon Weiswasser
N898JW

[RV6_flyer]

Originally Posted by jonweisw

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Anybody with some grey hair on this subject have any thoughts?

Jon Weiswasser
N898JW

Normal carbon / combustion by-product build up.

[Daver]

I bore scoped my cylinders on my used (450 hr SMOH) o-320E2A engine.

I also spotted some discolored patches.

I later removed one cylinder to inspect camshaft lobes. It all looks OK as far as
I can tell.

I wouldn't worry about it.

Dave
-9A finish kit
N514R reserved