I think the answer is in this month's Car Craft. They had an article on spray welding cast iron. Basically, you grind a "V" into the entire length of the crack. Put part into a gas grill or large BBQ grill. Preheat to 600 or 700 degrees F. Then use a special torch/welder combo that sprays powdered cast iron into the "V" notch. Fill the "V" with the special weld bead, then allow the part to cool in the BBQ grill no faster than 100 degrees an hour. Grind smooth and paint.

The powdered iron actually bonds to the casting the way that Brazing or Arc welding won't, so the weld will actually last through heat/cooling cycles without "popping". The article goes into much greater detail.

hope this helps

chip

Preaching the Hot Rod Gospel according to the 4-stroke apostles:

Suck, Squish, Fire and Fumes