I heard about Kroil 30 years ago from a mechanic at a coal fired power plant shortly after I started restoring old gas engines, (the single cylinder kind.) It is the best stuff I ever saw! Cast iron rusted to cast iron has always been a difficult problem to solve. I have a very rare Holland 1hp headless that was stuck badly. It took all one summer spraying, soaking, and tapping to get it unstuck but Kroil is the only thing I could find that would touch it! I didn't know about ATF/Acetone at the time, but it might have worked, too.
Best wishes,
Les
