*Chuckles* I know I shouldn't but I cant help myself..........speaking as a machinist and general smart arse the reason all Fuel class engines are all based on alum like T-6 and others instead of "good ole iron" is tensile to weight ratios while you could obviously engineer an iron block as strong or stronger then the current alum why in the hell would you? Alum blocks can and do make over 4k hp and are dead reliable at 60% less weight the failures sighted in alum Lsx's as far as I can tell have mostly been design/build failures not material failures hence the changes the CR5 team made along the way, to their blocks.anyway from a material view of course alloy iron has higher tensile properties then say t-6, however the tensile stress/es encountered in even a maximum effort road race engine are well with in range of duty for modern alum mixes, obviously for the success/es in all form of motorsports using various high output alum black based engines

As for the original topic question..........i dunno......