Blown head gasket, Cause?

[motor]

How can i tell what caused this gasket to blow. Im not sure if it was detonation,boost ect . Also wanted to know if i could get the Cometic gaskets direct from Cometic or somewhere else?
Thanks for the imput

 

[jd351]

Looks like a combination of boost and poor clamping. Check the head for warpage, and when you replace the gasket I would suggest using head studs instead of bolts. Torque the intake side of the head down 10-15Ft Lb higher than the rest as the intake bolts pull up on the head.