Skunk2 is proud to introduce its Pro Series XP (Extra Pressure) Racing Valve Spring Kits for the Honda K-series i-VTEC engines. Each kit includes Skunk2’s high-quality race-proven dual valve springs that are the result of nearly two decades of racing and engine building experience. “XP” features a higher seat pressure for turbocharged and extreme high RPM motors. This spring has a seat pressure of 100lbs @ 1.600” while keeping the coil bind height for higher lift camshafts. Each Pro Series XP Racing Valve Spring is manufactured exclusively from super-clean, chrome-silicone wire milled in Japan. By using inner and outer springs mated together through a slight interference fit and with differing frequencies, Pro Series XP Racing Valve Springs are able to prevent valve float and maintain valvetrain stability at engine speeds in excess of 11,000 rpm. Wound by a premier North American winder, our Pro Series XP Racing Valve Springs retains its durability and strength that results in improvement to the extreme fatigue limit of the wire and enhanced resistance to load loss. Pro Series XP Racing Valve Springs are engineered to handle the demands of extreme-lift camshafts operating at prolonged, high-rpm use at championship-level racing. Skunk2’s Pro Series XP Racing Valve Spring’s for the Honda’s K-series i-VTEC engines are simply the best on the market. Pro Series XP Racing Valve Springs have been tested at speeds exceeding 11,000 rpm on our engine dyno, street, and the race track. Our superior, Japanese-milled, super-clean chrome silicone wire is 100-percent eddy-current inspected prior to coiling. Next, they are heat-treated, shot-peened, and chemically polished for strength and durability. A special nitriding process concludes Skunk2’s rigorous manufacturing process.