Valve Stem Seals

KOK designs and manufactures valve stem seals for OEM engine applications in motorcycle, automotive, and heavy-duty platforms.

Valve stem seals play a critical role in controlling oil flow between the valve guide and valve stem, ensuring proper lubrication while preventing excessive oil consumption and combustion chamber contamination. Dimensional stability, material integrity, and consistent sealing performance are essential to long-term engine durability and emissions control.

Engineering & Performance

KOK valve stem seals are developed to operate under:

• Elevated engine temperatures
• Continuous valve motion and high cycle frequency
• Exposure to engine oils and combustion by-products
• Extended service life requirements

Seal design and material selection are aligned with engine architecture, valve train configuration, and operating temperature range.

Material Options

Available elastomer compounds include:

• NBR: standard oil resistance for moderate temperature applications
• ACM (Polyacrylic Rubber): enhanced heat resistance for higher temperature environments
• FKM (Fluoroelastomer): high-temperature and aggressive media resistance
• VMQ (Silicone Rubber): flexibility and low-temperature stability

Material selection is defined according to OEM specifications and engine operating conditions.

Dimensional Range

Min / Max Stem Diameter Range: 3.7 mm – 30 mm

Custom dimensions and configurations are supported based on customer-provided drawings and technical requirements.

Application Scope

KOK valve stem seals are specified for:

• Gasoline engines
• Diesel engines
• Motorcycle engines
• Passenger cars and light commercial vehicles
• Heavy-duty engine platforms