You could always cold weld it. What you do is drill a hole at one end of the crack, tap for pipe threads, install the plug. Then repeat, with the next plug about 1/4 into the previous plug, until the crack is completely sealed up. My Grandpa Shepherd used to do this, he had a quarter midget with a Continental engine in it that was repaired that way that used to thoroghly spank 2 engined go-karts at the races.
