Here's a better alterntive than JB weld. Use Devcon Epoxy Steel. It's sold by industrial supply places, and is considerably more durable and stronger than JB. I've repaired cracked blocks and other castings such as industrial pump housings, etc., and it gives very good results, IF the casting is thoroughly cleaned first. Bead blasting is good, followed by a steam cleaning or pressure-wash to get all the beadblast residue off. The epoxy must make a good bond with the pores of the casting, or seep leaks result. I've also seen a steel plate installed over a crack, by drilling and tapping a series of machine screw holes on both sides of the crack, and sandwiching the Devcon between the plate and the block. For an invisible repair of a crack, spread the epoxy evenly over the crack and press a piece of 40 grit sandpaper over the repair when it's about half-cured. The texture matches the casting surface almost exactly.
Jerry
