Cork-Rubber is the most frequently used material. FEL-PRO Blue Stripe premium-quality cork-rubber gaskets use evenly-sized cork particles evenly distributed throughout a rubber binder. The result is a compressible gasket without leak paths.
Fel-CoPrene synthetic rubber can offer longer life than cork-rubber. However, because it is more flexible than cork-rubber, it can be more difficult to install. Generally, a quick-drying contact adhesive should be used to bond the gasket to the valve cover before installation.
Rubber-Coated Fiber is used for some high heat applications, such as Chrysler big block V8 engines, where the valve cover is in close proximity to the exhaust manifold. These Fel-Pro gaskets are made of a stiff, high temperature fiber material coated with latex rubber.
Cork-Lam is used in applications where high vacuum or blowout conditions can be a problem. Cork-Lam uses a metal core with cork-rubber material chemically bonded to it on both sides. This construction allows for a thicker than normal gasket with exceptionally good torque retention and also allows for more clearance between the valve cover and valvetrain.
Composite Material is a superb choice for Pro-Stock, FunnyCar/Dragster, and NASCAR race engines. Laminated over a steel core, the composite material offers maximum compression and torque retention in super-high vacuum conditions. The Fel-Pro gasket is also coated with silicone for even greater sealability and easier removal.
Molded Silicone Rubber gaskets provide for ease of installation and are great for on again/off again situations like valve lash setting. These Fel-Pro gaskets feature high-tech silicone material for long life and sealability, a solid steel core for strength and durability, and stainless steel compression limiters to prevent overtightening. This is an excellent choice for high vacuum race engines.
whats the torque specs on these?
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