Steve: Thanks for your prompt reply. You certainly don't mince words. I also have never heard of a Mercedes engine going bad and I've had two and my brother two and I've known a lot of owners. Believe me no one was more surprised than I when this engine developed this knock. There was no mistaking it as other than a lower engine knock. As I said in my inquirey I knew the engine was a rebuild and if the engine#002xxx is correct it is an older engine as well. I can only wonder if the problem was one of sloppy rebuild or something else. I can guess that a less than accurate torqueing of the rod cap bolts could result in what appears to be the problem. The work was done in Texas (Austin area I believe) and there doesnt seem to be any way of finding out who did it, I wish I could just to see what their response would be. Thanks again, I guess I can chalk this one up to experience.