It is not overly common but have seen several come through the shop over last several years. Even did one on my own 94 craftsman about 8 years ago. I think it is do to the fact that is the thin area in the head gasket area and is subjected to the most ignition pressure. Will need to remove the intake manifold, blower housing, exhaust and the valve cover to get to all the head bolts, including the one hiding behind the spark plug. Torque the head bolts back to spec after replacing and adjust the valves to .004-.006 with the piston at 1/4 inch past top dead center compression stroke when done and you should be good.