What should I do if the valve of automobile engine is loud?

Engine valve noise can be made as follows: 1. Engine valve noise may be caused by valve air leakage, which is more obvious outside the valve chamber at high load and low speed. You can remove the cylinder head, grind the valve, check the valve spring force and readjust the valve clearance; 2. When the engine is idling, the engine valve response can be a continuous knocking sound between the tail end of the valve stem and its driving part. The solution is to readjust the valve clearance. If the lock nut on the adjusting screw is loose, it should be locked and the badly worn parts should be replaced. 3. It may be caused by rough surface of valve seat ring, unqualified machining accuracy, improper selection of interference of seat ring and excessive deformation of valve seat ring after heating. The treatment method is to reassemble the valve seat according to the requirements of assembly process, and the upper end face is flush with the plane of the valve body, and the higher part should be ground flat.