1969 Barracuda 340 Formula S Restoration
My exhaust manifolds have been inspected by High Tech Coatings and they said it was an adhesion issue with the base coat. The adhesion issue appears to be that the manifolds were perhaps soda blasted or cleaned with an alkaline cleaner that remained in the pores and neutralized the acid in the bonding agent of the base coat.
They are being completely stripped and redone at no charge.