After running in, the upper cylinder head, the hydraulic jacking rod and the rocker arm are also arranged in the original position, and the cylinder head is not provided with a valve body without gaps
I. valve clearance: when the valve is completely closed, the gap between the end of the valve stem and the component of the valve train is called the valve clearance. Two, the valve clearance is necessary: when the engine works, the valve will be due to temperature expansion, if the valve and its transmission parts, in the cold when no gap or clearance is too small, in the hot state, and the transmission of the thermal expansion valve will cause the valve is not tightly closed, causing the engine leakage in the power stroke in compression and the power down, don't even start easily when serious. In order to eliminate this phenomenon, the valve clearance is usually used in the cold assembly of the engine to compensate for the expansion after the valve is heated. Some engines use hydraulic tappet, the length of tappet can change automatically, and the thermal expansion of the valve is compensated at any time, so there is no need to reserve the valve clearance. Three, the valve clearance is too large and too small damage, the size of the valve clearance by the engine manufacturer, according to the test to determine. Generally in cold state, the clearance of intake valve is 0.25mm~0.35mm, and the clearance of exhaust valve is 0.30mm~0.35mm. 1, too small: if the valve clearance is too small, the engine in hot state may be due to valve closed lax and leak, leading to power down, or even valve burned.
