For the really serious, a differential cylinder pressure testing tool can be invaluable. This device, properly used, allows you to very accuratly diagnose valve or ring problems. I'm still surprised by the number of pro mechanics who do not use them or think that they're not worth the money. Peruse one of the many sites dealing with the care and use of one to find out the story. I wouldn't be without mine as a basic requirement for engine condition determination. Plus it looks really cool in use. Only thing is, when you read where it is possible to get hurt using one, let me assure you that THEY ARE NOT KIDDING.
Regards,
Ken Beckman
