When I reinstalled my engine I forgot to put the sacrificial anode in the top intake pipe. Is really all that necessary for an aluminum z head or should I put it in? Does it really save the head from damage?
It's a gimmick that does nothing but harm. As the magnesium anode dissolves it deposits corrosive magnesium oxide all through your cooling system. It's a very bad idea that does nothing to protect your engine, but will clog the radiator.
Considering the massive number of cars in service with iron blocks and aluminum heads, I would say that no sacrificial anode is necessary. Of course, the massive majority of those cars are running modern antifreeze solutions.
The most appropriate course of action is to contact the person who manufactures the head and follow his instructions...
I haven't had one in my Fordor for the last 28 years and have not had any leaks in the "Z" head yet so, I'm saying "no", it ain't needed.