Zippy is a factory guy, Perf Only is a pro engine builder, and I am a mechanical engineer. I agree with them. Welding cast iron is a real art and success is not guaranteed. NO WAY can it be done with the block in the car, with any reasonable expectation of success. cast iron is really special stuff and heating/cooling have to be rigorously controlled to avoid either the weld or the heat affected zone developing cracks.
Plus, if the hole is drilled and tapped wrong, how is welding going to fix that?
Also, welding will almost certainly tweak the block so that parts aren't square, cylindrical, etc.
How about stop-drilling the crack, drill and tap deeper for a long Helicoil, and use a longer bolt/stud? then torque to minimum.
R.
