Hydraulic or solid lifters. This is the hotter version of the popular viper camp. Has a sophisticated profile fast intake ramp with slower closing ramp for maximum cylinder fill. Requires springs with a minimum of 175/190 pounds seat pressure. Perfect combination with high compression 10:1 plus compression 80ci and small stroker. Provides very strong upper mid range with 6500 RPM top end power. Use with mild to wild ported heads, good free flowing exhaust, performance carb and ignition. So dig in for the ride of your life.