What is the appropriate valve clearance?
1 Answers
Valve clearance is determined by the engine manufacturer through testing. Generally, when the engine is cold, the intake valve clearance ranges from 0.25mm to 0.35mm, and the exhaust valve clearance ranges from 0.30mm to 0.35mm. Valve clearance refers to the gap between the end of the valve stem and the valve transmission components when the valve is fully closed. During engine operation, the valve will expand due to temperature rise. If there is no clearance or the clearance is too small between the valve and its transmission components when cold, the thermal expansion of the valve and its transmission components will inevitably cause the valve to not close tightly, leading to gas leakage during the compression and power strokes of the engine, resulting in reduced power. In severe cases, the engine may even be difficult to start. To eliminate this phenomenon, valve clearance is usually set during cold assembly of the engine to compensate for the expansion of the valve when heated.