When we say "out of the box," this is what we're talking about. Ports are already machined and ready for use, which means no port work is required. Hardened exhaust valve seats make for durability with unleaded fuel. Valveguides don't interfere with flow because they're positioned below the casting surface. Intake port sizes are 180 cc, 200 cc, and 215 cc. Chamber sizes are 58 cc and 64 cc. Intake valve sizes are 2.020 and 2.080 inches. Exhaust valve size in all cases is 1.600 inches. The new Pro Action heads are compatible with all original equipment and aftermarket performance parts (intakes, exhaust, valve covers, and so on).