The bmw heads (I had one) didn't crack because they were aluminum they cracked because they were a poor design which bmw fixed.

When you say "they" throw them away who are you referring to.

I have a friend with an airplane, I bet he doesn't throw his heads away.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.