Related Photo Galleries
Flat tappets can make power, but one of the limiting factors is in the corresponding valvespring. Too much spring load can overload the interface between the cam and lifter, and if the lifter is a hydraulic style, too much spring can collapse the hydraulic mechanism at high rpm. It's a paradox, because very intense valve action often requires high spring loads to control the valvetrain inertia, particularly if the valvetrain is on the heavy side. It's a tightrope to find exactly the right balance here, and at some point there simply isn't a practical combination that's workable, without extensive valvetrain lightening.