George at Clay Smit is the only guy i use. I have been going to him for years and years. He put my drag boat in the winners circle a few times. This might sound dumb, but did you check to see if you spit a chunck of exhaust manifold gasket out? I did that one time and thought I had a rod knocking. Was all bummed out and started to tear it down. Took off the headers and bingo. Chunk O gasket missing. You might get lucky too!