Valve stem seal | what does a valve stem seal do?

Although valve stem seal seems look a small part in the engine, it actually plays a very important role in it. It controls the amount of oil pass through the sealing lips to lubricate the interface between the valve stem and the valve guide of an engine.

If too much oil pass through the sealing lips, it would lead the engine lose the power or cause engine failure. If too little oil pass through, the valve would be not sufficiently lubricated and become worn. Because of the high temperature resistance requirement of the material of valve stem seal, MJ offers valve stem seal with FKM (Viton®), it can resist the heat up to 250°C.