Pro Magnum Hydraulic Roller Lifters Chevrolet Small block. For use in blocks originally equipped with hydraulic Roller cam. 1987 to present and Gen III LS1 LS2 and LS6. COMP Cams Pro Magnum Hydraulic Roller Lifters are specifically designed to perform at higher engine speeds. When engines are equipped with a hydraulic Camshaft high rpm is limited by the improper position of the internal piston as the lifter inevitably "pumps up". This improper location results in open valves and therefore leads to lost power or sometimes even engine failure. NOTE: These lifters require an adjustable valve train and must be pre-loaded to .002" to .004" for proper operation!