Thank you, I really appreciate the information. I am going to put a picture up of my piston I am replacing to get some input. It still had good compression (135psi) but when I loooked in from the exuast port Isaw, and felt a ridge on the front of the piston. I then pulled the head off, and saw some small pitting around the outside egde like something went through, but on the front of the piston there is a sharp edge peeled up about the same size as the exaust power valve. The tolerence is very close, but has anyone ever heard of the piston striking one? Like I said I will put a picture up tommorow. Thanks.