All good advice in this thread.

My ritual every 6 or so months is to take the engine out of the plane, remove the exhaust, the glow plug, prop. I then get a container and fill it with Marvel Mystery Oil. I then immerce the whole engine and exhaust in the container. I put in enough oil to just cover the engine. I let it sit 24 to 48 hours and occationally turn the crank and such on the engine to remove any gunk or dirt inside. I then take the engine out of the oil, let it drain, then just towel it off.

It keeps the engine casing looking like new and the insides look just as good as well. I have been doing this since 1984 and I have a few engines that are as old and have been cared for this way their whole life. I use the Marvel oil as an after-run oil as well.

Hope this helps somebody.