There are two basic lifter designs, a Flat Bottom and a Roller Lifter. The Flat Bottom lifter requires the use of a specially developed material that will endure the constant wiping pressure of the rotating cam lobe. The Roller Lifter converts that wiping force into a rolling force using a roller bearing resulting in a design that has less friction and a wider acceptance range of camshaft lobe profiles. Within both of these designs there are Hydraulic and Mechanical versions. Depending on the engine’s oiling system design, either type is capable of supplying oil to the upper valve train components.
(The Flat Bottom Lifter is pictured left, the Roller Lifter is pictured right)
Mechanical Lifters have no internal moving parts and have Zero effective loss in Camshaft Lobe Lift. This type of lifter requires there to be some initial valve lash to allow for thermal growth in the valve train. This valve lash will change over the life of the engine and usually has to be readjusted to maintain the correct amount designated by the engine manufacture.
Hydraulic Lifters have an internal piston assembly that is free to move within the outer body. This piston assembly moves to accommodate thermal growth and component wear to keep a net zero lash in the valve train. Once adjusted to the prescribed preload these usually never have to be adjusted again over the life of the engine.