340 X heads cracks between spark plug hole and intake seat

I have had cracked X-heads like that. One set I traded to a machinist buddy of mine and he fixed them. The other set I sold on here (yes, the buyer knew they were cracked). I currently have two sets with no cracks. Oh, and about old machinists, my buddy that fixed my old set was in his 20s at the time, maybe. He's 46 now...