i am going to assume mine is gonna need some machine work , plan for the worst hope for the best !!!! it's a tough old turd but it may be hiding something ya know . i still havent figured out my " knock " in mine . you hear it from start up , but softly , and its not a spun bearing sounds different for a lack of a better way to phrase it . it increases with speed , and yet i can run her hard all day and she'll be none the worse for wear . it won't even make any more noise than it did before . been through pumps , dizzy , all sorts of things . put a breaker bar on the no.3 cylinder though and put my ear on it and heard it plain as day . me thinks with pointers and info from all you i may have a bad piston pin , so some machine work is gonna be neccessary i'd assume . i'd rather spend the money and know it's right than roll the dice like i would with one of them belly buttons we ran in the dirt cars !!!!!!! probably can be done cheaper but ..............