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Engine Repair

Valve Stem Seals

Increasingly stringent emissions regulations make it imperative that oil not enter the combustion chamber.

These regulations, combined with today’s engines running hotter and valves opening and closing as often as 100,000 times an hour, make it necessary for valve stem seals to be made of the highest quality materials and latest technology to ensure a long-lasting seal.

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CONTROLLING EMISSIONS

Increasingly stringent emissions regulations make it imperative that oil not enter the combustion chamber.

These regulations, combined with today’s engines running hotter and valves opening and closing as often as 100,000 times an hour, make it necessary for valve stem seals to be made of the highest quality materials and latest technology to ensure a long-lasting seal.

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MATERIAL CHOICES

Valve stem seals are made from a variety of materials:

  • Nylon
  • PTFE rubber
  • Nitrile rubber
  • Polyacrylate rubber
  • Viton® rubber


Viton is the best material currently available for use in many of today’s hotter-running engines, particularly the smaller domestic and imported models. It is often combined with a “metal jacket” or covering that totally surrounds the Viton positive seal. Viton offers excellent resistance to both heat (up to 450 F) and abrasion, and is the material of choice for most Fel-Pro valve stem seals.

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SEAL DESIGNS

There are two basic valve stem seal designs: deflector (umbrella) seals, which move with the valve, and positive seals, which are fixed in position in the cylinder head.

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