I have been chasing a very minor but persistent oil leak on my IO360 in my 9A, and from the apparent location of it I was becoming concerned that I might have a cracked cylinder barrel. So today I took the time to thoroughly degrease the engine, making a respectable mess on the floor in the process, and then did a high power runup until my cylinder temps starting getting pretty warm. I shutdown and did the black light trick, and found my leak.
The picture below is of the #4 exhaust valve pushrod guide tube. A couple years ago I had dropped a cordless screwdriver onto it and dented it slightly - I made certain then that it did not contact the pushrod, and deemed it operable and kept going with it. Sometime later it developed a crack on that same impact spot, and that's where my minor oil leak has been coming from.
The picture below is of the #4 exhaust valve pushrod guide tube. A couple years ago I had dropped a cordless screwdriver onto it and dented it slightly - I made certain then that it did not contact the pushrod, and deemed it operable and kept going with it. Sometime later it developed a crack on that same impact spot, and that's where my minor oil leak has been coming from.