Intake runners are cleaned of casting flash but cast surface left intact to promote turbulence. Ports are matched from head to throttle body boots.
Exhaust ports are heavily machined to smooth the path as much as possible, diameter is left close to stock to keep gas velocity high. Mirror finish is desirable to prevent buildup of particulates.
Combustion chambers are machined as little as possible, but enough to remove any sharp edges that could be heat risers and promote preignition. Valves and seats are given 5-angle radius. Head is milled to true. This motor is already at near the limit for piston-to-valve clearance, so intake valves are slightly recessed in the seats to allow for milling.