When setting the valve clearances, I discovered that three of the adjusting screws were "galled" to their respective jam nuts. It made it very difficult to turn the nuts while holding the screw in position with a screw driver. So the next time I will have a new set of jam nuts which are cheap but I was wondering if the threads on the screws were buggered. If so, I'd like to consider running them through a tap to clean up the threads. Does anyone know the size and pitch?