AN ANATOMY OF
The Common Valve Stem Seal

Valve stem seals are small relative to other gaskets and seals in an engine, but play an important role in lubrication. What makes valve stem seals different than almost every other type of seal? The answer is simple they are designed to leak. Seals designed to leak may sound counter-intuitive, but the amount and way in which they leak is precisely controlled to achieve a specific goal.

Valve stem seals provide a controlled leak of oil to allow the valve stem to be lubricated as it slides in the valve guide. The amount of oil that passes by the valve stem seal must be precisely controlled, as too little oil causes stem and guide wear. Too much oil causes carbon buildup leading to valve seat damage, decrease in volumetric efficiency, increased emissions and excessive oil consumption.

There are two basic valve stem seal designs:

  1. Deflector seals, also called umbrella seals, deflect oil away from the valve stem. They are secured to the valve stem and move with the valve to shield the valve guide from excess oil. Umbrella type seals were commonly used prior to the development of positive type seals.
  2. Positive seals, attach to the valve guide boss and function as squeegees, wiping and metering oil on the stem as they pass through the seals.

seal-positive-metal-clad

Positive Seals - Metal Clad (Our Solution)
Not forgiving of guide O.D. variations. Uses garter spring for oil control. Excellent oil control properties. Can also be used with up to 0.003" oversize valve stems.

seal-all-rubber

Positive Seal - All Rubber (Original Chrysler Solution)
No rings or bands. Very forgiving of guide O.D. variations. Low temperature applications. Can also be used with up to 0.015" oversize valve stems.

seal-teflon

All Teflon Seals
Can be used in high temperature applications. Cannot be used without guide O.D. Cannot be used with oversize valve stems.

seal-top-hat

Positive Seals - Top Hat Style
Latest OEM style resembles a top hat in appearance. Incorporates valve spring seat in the seal carrier body. Often attaches to the guide for positive location. Excellent oil control properties. Can also be used with up to 0.003" oversize valve stems.

seal-ring-and-band

Positive Seals - Ring and Band
Less forgiving of guide guide O.D. variations. Can also be used with up to 0.015" oversize valve stems.

seal-1-2-ring

Positive Seals - One Ring and Two Ring
Very forgiving of guide O.D. variations. Can be used with oversize valve stems.

seal-ring-and-spring

Positive Seals - Ring and Spring
Very forgiving of guide O.D. variations. Uses garter spring for oil control. Excellent oil control properties. Can also be used with up to 0.015" oversize valve stems.