Spark plug threads, number 4 plug hole has some drag or minor cross threading on the last couple of threads. I just find it unsettling mostly because I pull the plugs a lot to evaluate things. When I pull number 4 out, there is resistance at first and resistance at the end going in plus I can see scaring on the spark plug’s thread when removed. I was going to chase the threads with a tap with a glob of grease on the threads of the tap like I was shown to catch any metal, but I do not seem to have that tap. Moreover, I always like to hear from others on something like this. Oh and thanks Tex for the oil suggestion; it does seem like a waste to drain so quickly. The oil and exhaust are or so clean on this rebuild that I like to contribute it to that 4th ring below on the piston, but it is still too early to tell anything and pride doesth proceed the fall.