hey all you engine guys, I have a question, I have one cylinder on a six cylinder Lycoming engine that started to make oil quite badly. This came on fairly sudden, it will load up the plug with oil fouling in a couple of hours. If the plane sits for a day or two I will have liquid oil pooled up on the bottom spark plug.
I suspected a broken oil wiper ring but pulled the jug and it is fine. All the rings are fine. The compression tested OK. I can find no excessive slack in the valve stem. I will clean up the piston and the jug for a closer exam but have any of you got any idea that I have missed?

Shane

Do not rule out valve guide wear at the stem. Not sure what you are referring to when you say valves show no excessive slack. Do you mean the guide clearance? Lycoming does tend to oil starve the top end at times leading to the wear of valve guides. The following is a suggested test by a professional troubleshooter. It might provide some insight.
http://www.littleflyers.com/Questions/l ... ycO540.htm