Description: Dyno-tested on a 383 cu. in. engine, Trick Flow's Kenny Duttweiler signature series 23 Degree heads made 460 HP and 451 ft.-lbs. of torque--40 more HP and 11 ft.-lbs. more torque than the same engine with new GM L98 Corvette heads. The 23 Degree heads also made more power than Dart Iron Eagle and World Products Sportsman II cast iron heads. The 23 Degree heads are a direct high-performance replacement for most OE factory heads, and accept most factory accessories. They feature a choice of 62cc as-cast or 64cc and 72cc CNC-profiled combustion chambers, stainless steel 2.02 in. intake/1.60 in. exhaust valves, hardened exhaust valve seats for unleaded gas, and 195cc intake ports with a high-velocity, small cross-section design to promote low rpm torque without sacrificing higher rpm horsepower. They come fully assembled with valves, valve springs, locks, retainers, rocker arm studs, and guideplates, and are 50-state emissions legal.