The product description：
When engine works, the valve transmission parts will expand and extend due to heat. If there is no clearance res erved, the valve will be opened and air leak is caused; if there is clearance reserved but too big, the clash and abnormal sound will appear and abrasion is caused.
Valve clearance is adjusted by lifters or rocker arms which are components of valve train. Lifters are cam followers which can pass the movement and acting force from cams to push rod or valve, and meanwhile bear lateral force imposed by cams and pass it to engine body or cylinder head. Valve clearance is compensated by adjusting bolts or spacers for mechanical lifters which should be regularly checked and replaced due to abrasion.
Hydraulic lifter can realize zero valve clearance by automatic adjustment and compensation when valve and its transmission parts expand or shorten due to temperature rise or abrasion, so it is also called valve clearance automatic compensator.
