I've done a lot of crack patching, and the most effective stuff I've found is a product called Devcon Epoxy Steel. It's similar to J-B Weld, but it's for industrial use. Try drying the block out with a propane torch in the area of the crack. If any water seeps under the patch while the epoxy is curing, it will keep it from bonding to the block properly. Ditto on leaving a rough surface, and get the block ground down to clean bare metal for 1/2" or more on all sides. If you want to hide the repair, press a piece of 40 grit sandpaper onto the surface of the patch when it's about halfway cured. The sandpaper will leave a rough surface that resembles the texture of cast iron. Good luck!
Jerry

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