Assuming that both ends of the crack are visible, it is normally possible to salvage an iron head by gas welding. For best results, the casting should be preheated to 1200 F. Skilled TIG practitioners can do the same for aluminum heads.
Some shops prefer to use one of several patented “cold stitching” processes on iron castings. The technician drills holes at each end of the crack (to block further propagation) and hammers soft iron plugs into the void, which are then ground flush. The plugs must not be allowed to obstruct coolant passages.
Metal spraying is demonstrated to have utility, but rarely practiced.
