Saw an interesting process on a British show, Car SOS, on Friday Night 3rd Feb. around midnight. A cylinder head had a crack in the water jacket on top of the head, where there is a raised section like a pipe that goes to the radiator, that had the crack in it.
How it was done was called a cold welding process, that entailed cutting out the cracked section and replacing it with another piece of cast metal, this was hammered in, then cut across the joins, clips inserted and a special type of screw inserted.
The whole repair section was then filed flush, to look very similar to the finished head.
Tried to find a You Tube Video of it but all entailed a welder.

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