How normal is the automobile valve clearance?

Cars generally adopt the following valve clearance specifications: 0.25-0.30mm when inhaling and 0.30-0.35mm when exhausting. However, the gap between different models may be different. The expansion of the valve is caused by the temperature rise when the engine is working. If there is no gap between the valve and its actuator in cold state or the gap is too small, the power will decrease due to the expansion of the valve in hot state. In order to eliminate this phenomenon, a certain gap is usually left between the valve and the actuator when the engine is cold assembled to compensate for the expansion of the valve after heating. Some engines use hydraulic tappets, and the tappet length can be changed automatically, so the thermal expansion of the valve can be compensated at any time without ensuring the valve clearance.