Head flow,vs. cam lift?......

current cylinder head rule for SS....

CYLINDER HEADS (April 15, 2013)
Must be correct casting number for year and horsepower claimed,
per NHRA Technical Bulletins or NHRA-accepted. Cylinder-head
casting must also be on NHRA runner volume list as published on
NHRARacer.com. Porting, polishing, welding, epoxying, and acid-
porting permitted. Grinding and polishing in combustion chamber
permitted. Welding and/or applying epoxy in combustion chamber
prohibited. Spark-plug hole must maintain the stock location, size,
and angle as machined by the OEM; spark-plug adapters
prohibited. Valve-guide centerlines must maintain the stock lateral
and front-to-back location as machined by the OEM. Valves must
maintain stock angle; valve-stem angle must remain stock, +/- 1
degree. Cylinder head must be able to hold combustion chamber,
intake and exhaust runner volumes per NHRA Specifications. Any
aftermarket steel valve permitted; must maintain stock head and
stem size; titanium valves prohibited. (OEM sodium-filled valve may
be replaced with titanium, provided weight is equal to or greater
than original.) Valve diameter permitted to be +.005-inch or -.015-
inch from published NHRA Technical Bulletins. External
modifications prohibited, intake side of head may not be cut into
any part of valve-cover bolt holes (except for SS/AH). Valve-cover
bolt holes must remain unaltered and in their original location
(except for SS/AH). Welding or epoxying permitted on external
portion of runners for repair only, maximum 2 runners per head.
Heat riser passages may be blocked off from intake-manifold side
of cylinder head or in exhaust port. The following are permitted:
polylocks, jam nuts, screw-in or pinned studs. Any valve job
accepted. Exhaust plate permitted between header and cylinder
head, maximum 1/2-inch; may not protrude into exhaust port.
Cylinder head may have all seats replaced.