They were installed in an engine with less than. 700" lift with spring pressures of 240+lbs on the seat and less than 600lbs open. The springs are changed each season. Also, relatively low lift cams and spring pressures.
Manley 221442-16 Polished NexTek Oval Track Endurance Valve Springs 1.560" OD
Manley 221440P-16 Polished NexTek Oval Drag Race Valve Springs 1.570" .700" Lift
Manley 221443-16 NexTek Oval Drag Race Valve Springs 1.580" .730" Lift
Manley 221444P-16 Polished NexTek Oval Drag Race Valve Springs 1.610" .750" Lift
Manley 221424-16 NexTek Drag Race Double Valve Springs 1.640"OD, Used, Excellent
Manley 221424-16 NexTek Series Drag Race Valve Springs 1.640" .880" Lift Set 16
