Anyone ever break/bust/crack/fracture the factory 273 adjustable rocker arms?

can you say bulletproof? Ductile iron is cast, not forged but is hardened by a process to make it more impact and fatigue resistant than pig iron. Its very difficult to forge iron.
Right, that's 'cause they're forged steel, Crane offered ductile iron rockers tho'. I read a
bunch about the modified nodular iron used in the new drop spindles out there.............