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The IO–360-A1B6 engine in our RV–8 has been making some metal. I first noted it when inspecting the oil filter after an oil change in August - I found roughly 50 shiny, ferrous flakes. I consulted Lycoming SI–1492D, which describes various types and amounts of metal one might find in an oil filter, and recommends action. Based on that recommendation, and after consulting with three Aircraft Maintenance Engineers (an AME is the Canadian equivalent to an FAA A&P), I flew the aircraft for two hours and checked the filter again. I counted 7 flakes, so I flew 10 more hours (I was away for most of the rest of the year, so this took until January). This time I found the rate of making metal had gone up quite a bit, and now I was seeing what looked like aluminum along with the steel, so I grounded the aircraft.

When I first found the engine was making metal, I feared it could be the cam. After finding aluminum too, I did some research, which lead me to wonder if it could be a broken piston ring.

I acquired a Vividia VA–400 borescope, and today I took a look in the cylinders.

Three cylinders looked pretty good, but #4 has a very strange, wide area where the cross hatching is not visible. This area goes all the way up the cylinder.#4 cylinder

 


At first I thought it might be a piston pin issue, but I’m pretty sure it is no where near the front or back of the cylinder (you can see the top plug hole, with borescope shaft through it, in the second photo). The next step is to find an AME to help me pull that cylinder to investigate.#4 cylinder

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