Why don't you follow the engine instructions and put some oil (preferably caster oil) on the threads and torque it up. The oil will react to the heat and sort burn in a nice hard thread lock. But do not put Lock-tite or you will eventually regret it. Just run the jam nut up tight when it is cold and make sure it is still tight after a run and the oil will do the trick.

Cheers,

Chip