I have never had trouble with the jam nuts. Some people just tighten things as much as you can. If you are one of these types I would suggest going to an industrial supply store and by some high strenght nuts. I had an OS, poor performance when propping below 9K, I proped the OS .91 for 9,500 to 9,800. But the TT likes to run over 10K on the ground. Those extra revs are bound to have some effect on the valve train, however I never had a problem except with a loose screw on the rocker cradle, the screw broke and the cradle came loose, TT replaced it under warrenty and a little Loc Tite keeps that from happening again.