The function of the valve guide is to guide the movement of the valve so as to ensure that the valve reciprocates in a straight line so that the valve and the valve seat can be correctly fitted and the heat of the valve stem can be transmitted to the cylinder head.
Valve guide working temperature is higher, about 200 ℃. Valve stem in the catheter movement, only by the valve body splashed oil lubrication, so easy to wear. Therefore, the use of self-lubricating properties of ductile iron or powder metallurgy materials made of separate parts, with a certain amount of pressure into the valve cover on the cylinder valve seat hole to prevent the fall off. Some engines use a snap ring to secure and position the catheter to prevent loosening of the valve guide.