I'm no expert at all, and will also run alum heads in the future, but the whole iron/alum myths have always bugged me because so many things get repeated without backup info.
Combustion is complicated, and alum vs iron definitely has an impact but it seems to be in different ways than 'common sense' would seem to suggest. I'm still digging through the occasional engineering or research paper where I can - always fascinating stuff to find.
