Let's do the smell test:

GM builds real crate engines that they extensively test and attach a warranty to those engines. They have access to resources that the common man couldnt begin to have. The GM 12498827 engine is 572 ci at 12:1. It has an advertised HP of 720@6250 and a TQ of 685@4500. This aint Leroy's Crate Engine Shop down the street either. They make a low compression model too.

Given that GM tests/designs/develops/manufactures heads in both iron and aluminum (and some stuff we arent told about), doesnt it smell right that they would choose a head that maximizes performance? Maybe not emissions or gas mileage on this part number but certainly performance. If an iron head made more power, they would have used it. If there was a lhint of a ongevity issue with aluminum in a 12:1 motor, they would have used iron.

mike in tucson