Since people are still posting advice about high-cost, high-skill techniques for cast-iron repair, here is a technique (mentioned in my post, above) that has many advantages over more "traditional" techniques. I had this type of repair done on a relatively rare intake/exhaust manifold-assembly a few weeks ago. THe part was repaired after few hours of labor, and very little expendable-material, and a far simpler procedure than necessary for other techniques.
This technique has been around for about 40 years but never caught-on until recently:
powder welding (flame spray welding) of cast metals spray-weld repair of a GMC COE cast-iron carb heater planed mating-surface of repaired part It looked to me that this technique requires much less operator skills that other welding/brazing techniques.
As I mentioned above, the person who did the repair for me also inspected a 235 block with a 20+ inch crack along the bottom edge of the block (along the base of the water journal). He said that the crack in that location could be easily and reliably repaired. He also said that it would be cheaper to find a new block.
