Cometic C9825 Copper Cylinder Base Gasket 3.8125" Bore .020" Thick Big Twin 1984-Up 2-Pack

The Cometic C9825 copper cylinder base gasket is designed for Harley-Davidson Big Twin engines from 1984 and up with a 3.8125-inch (3-13/16") bore. This 2-pack provides premium sealing performance for high-performance and big bore engine applications.

Key Features:

• Premium solid copper construction for superior heat dissipation and sealing
• 3.8125-inch (3-13/16") bore diameter for big bore cylinder applications
• .020-inch compressed thickness allows precise deck height adjustment
• Ideal for builders who need to fine-tune piston-to-head squish clearance
• Heavy-duty design handles extreme heat and combustion pressure
• Compatible with Harley-Davidson Big Twin engines 1984 and newer
• Includes 2 gaskets per package

Copper base gaskets are the preferred choice for custom engine builders and performance applications where precise cylinder deck height control is critical. The soft copper material conforms to cylinder and case surfaces, creating an excellent seal even with imperfect surface finishes. Multiple thickness options allow builders to adjust compression ratio and squish band clearance for optimal engine performance.