Excessive oil can affect engine emissions and performance while insufficient oil quantity can affect durability In its most basic function, a valve stem seal is simply a wiper.

The sealing lip wipes oil off of the valve stem as is oscillates up and down in the valve guide. However, due to the need for lubrication below the seal, the amount of oil that is wiped off the valve stem must be controlled. There are a number of factors that go into determining the amount of oil that will be metered past the seal at a given time.

In addition to the sealing lip, there are other elements to the valve stem seal important to its design. The operating environment of the seal will determine the rest of the seal design. The oil type, operating temperature, pressure, valve train geometry, engine type, desired seal life, valve spring design, assembly method, and cost will all have an effect on the design and actual function of the valve stem seal in the engine.

Corcos is currently able to produce 17 different shape of valve stem seals using a wide variety of compounds. Such a wide choice is necessary to be able to fulfill any request from large tolerances to specially small housings, from long endurance to special applications. Current products already fulfill new environment regulations that will become laws over the next years and development goes on continuously to develop even better product before any law compels to do so.