Ferrea Competition Plus Exhaust Valve - Honda D16Z6/D16Y5/D16Y7/D16Y8 Stock Size - Set of 8 - F1821PFerrea Competition Plus Valves have built a reputation as the industry's most reliable extreme duty valve. To manufacture the valves we use special aerospace quality alloys, including the EV8 Z18, which provides high tensile strength. An exclusive two step slow forging process ensures proper grain flow and virtually eliminates any damage to the material structure. The valves are then heat treated and stress relieved over a 48 hour period, which is the