High Energy Hydraulic Flat Tappet Lifters. Patented orifice metering valve precisely meters oil to the Rocker arms. Continuous contact between the metering valve and Pushrod seat is maintained: Eliminating excessive oiling at high RPM. Pushrod seat is made of a special powdered Metal iron alloy that is heat-treated for strength and wear resistance. Longer piston than conventional hydraulic lifters, which provides more load bearing surface and increases lifter longevity. Lightweight check valve disc allows for quicker response, which results in increased engine speed before valve float. Lightweight check valve disc maintains added control at all engine speeds and loads. Applications Buick 181-252 Odd-Fire V6 ('78-'88) and 198-225 Even-Fire V6 ('62-'67).