Hi there valve clearance is an important part of vehicle maintaince, (see below for more details) the check procedure is fairly basic, the adjustment is some what more complex, the check should be done every 30, mils, but the adjustment may not be required for some time.
Heat produced in the engine causes internal engine components to expand and contract. As the engine heats up, proper valve clearance is essential for optimal performance.
Engines are made of many different materials and metals. Each material expands at a different rate and each engine component is subjected to different levels of heat. Manufacturers design engines to have space between components so that the various components can rotate and function.
To avoid premature wear of internal engine components, it is critical to maintain correct valve clearance. Incorrect clearances can cause the engine's intake and exhaust valves to fail prematurely, which can lead to engine idle and drivability problems, as well as excess pollution.
The recommended interval for checking valve clearance varies among manufacturers. To check and adjust the valve clearances, the valve cover is removed, the engine is manually rotated, and each valve clearance is measured and adjusted as required.