Big Block Cylinder Heads "915 vs 906"

'1970' 383/335 HP

The 1970 383 came thru with 9.5-1 Compression Flat-Top Pistons, and
the deck height was below the deck {-.004}, per factory minimum specifications.

These 383 Engines never had a problem when swapping on a set of #915 {Closed Chamber} Cylinder Heads.

Since the Piston {when it left the Factory} was down in the hole about {-.030"}