Well since I'm too blue (get it??) to post in the diesel forum /forums/images/graemlins/frown.gif, I'll do it here. I finally found what was causing the fuel knock ing the ole 6.2. I pulled the head off and the pre-combustion chamber fell out /forums/images/graemlins/shocked.gif. It still fit good, but wasn't snug and was allowing a compression loss around it. I took out an old pre-combustion chamber from a head I had replaced last year and installed it in this head. It fits nice and tight /forums/images/graemlins/thumb.gif. I hope to get it all back together over the next few days after a long time of frustration. I was real relieved to see the mirror finish on the cylinder wall and that the piston still looked good /forums/images/graemlins/waytogo.gif.