Will the wear of the contact surface between camshaft and rocker arm lead to excessive valve clearance?

It will cause excessive clearance and make the engine sound louder.

When the engine is working, the valve will expand due to the increase of temperature. If there is no gap between the valve and its transmission parts in the cold state or the gap is too small, then the thermal expansion of the valve and its transmission parts in the hot state will inevitably lead to the untidy closing of the valve, resulting in air leakage in the compression stroke and power stroke of the engine, thus reducing the power and even making it difficult to start. In order to eliminate this phenomenon, when the engine is assembled in cold state, a certain gap is usually left in the valve and its transmission mechanism to compensate for the expansion of the valve after heating. This clearance is called valve clearance.

The wear of the cam and rocker arm will lead to a larger valve clearance, which will not only affect the normal valve timing of the engine, but also make the impact between the transmission parts and the valve more intense with the increase of the engine speed, so the abnormal sound will become larger and further wear between the valve transmission parts will be aggravated.

At present, the engine basically adopts hydraulic adjustment structure, and the valve clearance is automatically adjusted by adjusting the oil pressure in the oil cavity inside the tappet. Of course, if your engine has no hydraulic tappet or adjusting structure, and the valve clearance increases due to the wear of parts, you must manually adjust the valve clearance to slow down the further and more serious wear.