In order to ensure the normal operation of the valve train, the relative angular position of the cam on the camshaft has strict requirements. The relative angular position of each exhaust cam of the same cylinder ensures the valve phase in a working cycle; the relative angular position of each cylinder’s intake (or exhaust) cam should be consistent with the ignition sequence of the engine. Therefore, as long as the rotation direction of the camshaft and the working order of each intake cam (or exhaust cam) are known, it is not difficult to judge the ignition sequence of the engine. For the camshaft of the four-cylinder four-stroke engine, the angle between the cams of the same name is 360W=60/6=60 for the four-stroke six-cylinder engine. The camshaft is usually driven by the crankshaft through a pair of timing gears , When assembling the crankshaft and camshaft, the timing marks must be aligned to ensure the correct valve phase and ignition timing. In order to prevent the axial movement of the camshaft, the camshaft must have an axial positioning device. The cams of modern automobile engines mostly use thrust flange positioning devices. In Jiefang CA6102, Dongfeng EQ6llJ, Toyota ZY, and 3Y camshafts, this positioning method is used, that is, the thrust flange is installed in front of the first journal of the camshaft. On the boss, the boss is thicker than the thrust flange to ensure that the axial clearance between the thrust flange and the timing gear meets the regulations (0.05~0.10S for cars).