Some of these posts have made me scratch my head. I will attempt to straighten out some things I think I know about.
1) Aluminum OHV heads have been on gas engines for at least 50 years, some with better results than others. They aren't new.
2) Aluminum melts at 1280 f. It will not magically stay solid at 1600. That is why the crucial number on anyone's exhaust gas gauge is 1150, since it is downstream from the event. Any higher and you are looking at pistons with holes in the top.
3) The galvanic reaction can happen to some extent, depending on several variables. There are millions of aluminum heads on cast iron blocks that have a useful service life of 200,000 miles and more.
4) Aluminum and cast iron have a very similar expansion rate. At normal operating temperatures it insignificant. Molten aluminum has a shrink rate of .007 per inch, cast iron is about .010 (Iron melts at almost double the temperature of aluminum). Those numbers change a little in the casting process depending on shape and length, but are close enough that all of the automobile manufacturers have decided it is OK to use dissimilar metals in engine construction.
5) There is a significant difference in head porting and polishing. What Gary does is an aggressive polish job that undoubtedly helps air and exhaust flow, especially for the turbo engines. A port matching job is not necessary for the IDI simply because we do not have the concern the gassers do about atomization and fuel pooling. A smooth airway is all we need.
6) What good does it do to talk about not ******* in other people's cheerios and then go ahead and do it anyway? Your opinions count as much as anyone else, but don't wrap them in a **** sandwich. They lose their taste.