i think you should look into the timing chain answer you got, if still nothing, time to pull apart the bottom end.... maybe you had a bearing expand from the heat... if thats the case, you might have to just have your crank turned, a new set of a bearings, and a new gasket set... but it'd be cheaper than buying a new motor........ worse comes to worse, you'll find something really really nasty in there, and realize its time to upgrade to a 600HP crate motor