Edelbrock RPM head casting flaw

I would just call them and ask and while you have them on the phone tell them what happened...they might not give you a new head but could offer some kind of concession although doubtful. An old timer told me that defects occur more often with edelbrock head than other brands. I run edelbrock heads..came with the engine when I bought it; so far so good.

Anyone know what type of aluminum the heads are cast of?