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I think I mentioned this before. Use irontite tapered plugs. Magniflux to see where the crack goes then drill a hole at the end of the cracks so they won't travel anymore. Then stitch it with irontite plugs overlapping each one. You have to drill the hole, tap it with a tapered tap. You dip the plug in the irontite solution. Screw it in till it snaps off. When done you can grind it down to make it look nice and then paint it. Done. I have done a few hundred of them when I was in the machine shop trade, in the shop or on the road. Very good success rate.

If the crack is on the outside like you show then it can be repaired easily. I have repaired 50 or 60 blocks like this. I am retired now for a long time but if you stitch it with iron tight tapered plugs it will be fine. Just remember to drill a hole at each end of the crack so it does not expand. Then start in the center and work to the edge overlapping each plug. Then go the other way to the edge. There are different size plugs that you can buy if you do it yourself or you can take it to an automotive machine shop that will do the stitching. I would not use heat (welding) unless you know what you are doing. Cast iron and welding do not mix and you would end up with more cracks. Just saying. I have used reverse polarity (cold welding) and it has worked but not as good as stitching. I hope this helps. rdub