elm I was told how to do the JB thing by a jent that was a machinest at NAPA and a flat track racer [with chev 6's] The JB thing works but you must cleanit very well. The big prob is getting the stuff to stay where you put it, I was told to lay block so you could form a puddle over the crack/ and POUR IT IN PLACE and wider than the crack by 1/2-3/4 inch and about 1/8+ thick [in depth] . then DONT MOVE, TOUCH, SPRED,for a few days. This method is for water jacket rust threw only. not for cracks in areas like main webs or areas of stress.
