Well, I picked up the block today after work and got it home on the engine stand. Using a 4 inch grinder with a fine wheel, I ground out a small groove in the crack to about 1/2 inch past where I could visually see the crack end. I then cleaned it with Brakleen, air hosed it off, wire brushed the heck out of it with a new stainless steel wire brush.
I agree that MIG is really not the best means of welding cast iron. It is supposed to be down with nickel rod, so I am told by a pipefitter friend whom welds at a nuclear plant for a living.
Atfter preheating the side of the block with a rosebud tip from the oxy/acetylene torch, I tried to MIG the crack closed. IT was going well, except when i finished the bead, I could hear it cracking, and see cracks across teh bead. Cast iron is a funny material, not very stable at all.
pic of the welded crack. I had spoken with the machine shop owner, he had another 4bolt main 350 block that was his sons and he offered it to me for $250.00 if I would let his shop do the machine work on this block as well. He felt bad about not finding the crack earlier and does not hold me liable for the work. I thought that was a stand up thing for him to do. I agreed to let him bore and hone the second block. Paid him for it and took my boat anchor home to try welding it. (I think in the back of my head I already knew it wasn't going to work.)
