Keith, the crack repair method is called irontite, a series of tapered cast iron or alum plugs. They are installed at intervals and when the crack is covered worked back in the intervals so that they are lockstitched, a sealant is used and plugs are screwed in till they snap off and peaned and ground. An insert can then be fitted if it was in the combustion chamber and had cracked seat. A very successful method with right operator, but really only used these days on hard to find components. Get a good b20 like the guys say and you wont be having nightmares about repaired cracks going wrong.