Had that prob on another machine. I got the engine running, found out they overheated it, made new carb gaskets, installed new intake gaskets, engine ran perfect, they loaded 2 trucks about 3 hrs, then went to s**t again, now it starts alright but spits and sputters when revving up the engine, going to put timing light on and see because now its binding when turning over, removed distributer, cleaned and checked, no difference.