Skunk2 311-05-7380 Pro XP Valve Springs K20A - K20A2 - K20Z1 - K20Z3 - K24A2 - F20C - F22C Engines Seat Pressure: 100 lbs at 1.600? - Open Pressure: 255 lbs at 1.100? - Coil Bind: .890? - Max Lift: .680? Must Use Skunk2 PN 312-05-0010 (Spring Bases) to Install Dual Springs in Single Spring K Series Heads or Install K Valve Springs in F20C/F22C Engines