Pre -heat head
 

Recently cracked a head while filling cross over of a 6x head ,the other head didn't crack,pre heated both heads.maybe the one that cracked wasn't heated high enough,which brings me to my question, What should the pre- heat temp be prior to adding the moulting aluminum?

250 should be plenty good, but you need to cool it down slow over the course of 6 hours if you don't not want to have to do some re maching!

Pre-heat to 450-f was my goal when doing this. Let it sit in the oven or gas grill for at least an hour to ensure heat has soaked evenly through entire casting. Hotter head means slower cooling of the aluminum which ensures more consistant grain structure. Also helps expel any moisture that may be present in the porous iron.

Thanks GRX,oven would work better for me.That or will try Contronics 940 ht ceramic