[Mister Moose]

The sand blasting or wire wheel gets you a clean surface, the V-out of the groove improves mechanical adhesion, but the V should extend only partially into the block thickness. Your best repair is to do both. A die grinder with small abrasive bits will clean up the crack area to bare metal with no sand, and give a cleaner surface than a wire wheel. You want bright metal clean, and you want grip. Clean and epoxy a bit past the visible end of the crack as well.