The valve lifters which are simply called as lifters follow camshaft lobe in the motor engines and function to close and open the valves in an engine. These are available in different formats and sizes. The selection depends on the camshaft that a lifter will ride upon. There is a form of hydraulic lifter that works with both flat tappet and roller tappets. These are also available in the more solid mechanical form for flat and roller types as well.
Each format of valve lifter has its pros and cons with it. Hydraulic flat lifter costs least among any format and are easy to handle. This is the reason that these are most widely used. They use oil pressure to move the push rods and ride on the camshaft's lobes. The best aspect of this type of filter is its ease to handle and maintain. On the other hand the major disadvantage being the revolution frequency and capability to pump up the valve with high engine revolutions per minute.
The mechanical valve lifter have similar type of working as that of hydraulic flat lifter, the difference being its pre-determined ability to drive the valve. It is quite expensive and also quite noisy. It requires continuous adjustment to ensure smooth woorking.
The roller valve lifters consist of steel wheel at the base of the lifter. This wheel operates along the camshaft's lobes. The machine is designed in such a way to produce minimum friction and maximum horsepower. Roller lifter is quite efficient and produces high horsepower along with saving fuel.