I spent much of the day at the airport, and finally finished the annual inspection. I found and fixed a few little things, the most significant being loose connections on the starter power cable and the engine ground strap. These slightly loose connections may possibly explain why the engine wasn’t cranking quite as nicely as it big a year ago. We’ll see.

I also found blue fuel stain on the inboard end of the right fuel tank. There isn’t an active fuel leak, but there certainly was a leak at some time in the past year. I’ll keep an eye on that one. Hopefully it’ll make it through the winter, as it’ll be a lot easier to fix this in warm weather when Proseal will cure properly so I could deal with it without removing the fuel tank from the wing. I spoke with a multiple aircraft builder and Aircraft Maintenance Engineer who said that he had experience with fuel leaks that appeared to fix themselves. His theory is that the blue dye may eventually plug the leak.

I was concerned by a strange grey discolouration I found on the lower left engine mount and also on the starter cable that runs in the same area. It looked a bit like exhaust stain, but that area was a long ways from any possible exhaust leak. I was afraid at first that it might be a sign of a cracked cylinder, but the cylinder had no discolouration on it, and I couldn’t see any cracks. And, the discolouration wiped right off, unlike the exhaust stain that resulted from the broken exhaust leak I had last year. I eventually traced it to some fretting that is occurring between the front side of sliding oil cooler door and the oil cooler mount. The air flow that leaks between the front of the oil cooler door and the oil cooler mount would carry the small amount of aluminum residue from the fretting, and that air path comes out right next to where I saw the discolouration.

I advanced the ignition timing 5°. This model engine originally had an ignition timing setting of 25° BTDC. After a few years, due to issues with high CHTs in some installations, Lycoming suggested an optional ignition timing change to 20° BTDC. I set my timing to 20° before the first flight, and hadn’t changed it until now. My CHTs run quite cool, so I decided I would try 25° BTDC. In theory, there should be a bit more power with this ignition timing. I’ll do some performance testing to see if I can detect any difference.

I hope to get flying tomorrow morning. The weather should be good. Hopefully the runway won’t be too icy.