Copper Header flange gaskets
My theory was if there is no gasket. Then none can blow out. Both surfaces have to be flat and smooth, Always slice the header flange between the front and center two and the rear and center two pipes if they have one piece flange. This allows for expansion.
This is the main reason they sell two and three piece manifolds for the Cummins Diesels. Lets everything move together. Diesels expand so much they shear the bolts off. We are always removing some at the shop when doing heads.