Big Block Cylinder Heads "915 vs 906"

RustyRatRod said
The 67 915 was not the only 915. There was a 915 that had the small 1.6 exhaust valve, too. Now whether the ports were the same, I have no clue.

The #915 Cylinder Heads with the 1.60" Exhaust Valves had nearly
the same Port Sizes {claim of identical}, but the Exhaust Valve 'bowl
area' below the Valve Seat was smaller.

The Exhaust Ports on the 1.60" Exhaust Valve Heads flow at
approximately 20 CFM's less than the 1.74" Exhaust Valve Heads.

The Intakes are 'near identical'.