Valve Cover GASKETS


Valve Cover Gasket Function
Much like oil pan gaskets, valve cover gaskets come in all shapes, sizes, and designs. Valve covers are also sometimes referred to as cam covers on overhead cam engines. On some engines, there are additional covers that allow further access to the valvetrain.

Valve cover gaskets, over the years, have ranged from low cost cork-rubber parts to some ultra-sophisticated molded rubber parts. Some have steel reinforcement, while others have plastic structures. Compared to oil pan gaskets and other cover gaskets, valve cover gaskets must fulfill these additional requirements:

Valve Cover Gasket Materials and Designs

Cork-rubber material quality is critical to the lifespan of the gaskets. Performance can vary depending on cork particle size, the choice of rubber compound used and the percentage of reprocessed material blended with virgin material.

In the 1960's, around the same time that cork-rubber gaskets began replacing plain cork in the marketplace, solid rubber gaskets die cut from sheets were also introduced. These rubber valve cover gaskets supplied by major gasket brands performed satisfactorily on conventional valve covers, when installed per instructions. Magnum has chosen to supply a premium grade cork-rubber material for conventional valve covers, because it is cost-effective and less sensitive to installation techniques than die cut solid rubber sheet.

There are also specific engines with a tendency to develop "hot spots" on the cylinder head gasket surface. One example is the Small Block Chevy V8. It has cylinder heads with back-to-back exhaust valves that create a hot spot when the engine is running under heavy loads for an extended period such as pulling a trailer up a mountain. Magnum offers optional Cork-rubber gaskets with special heat resistant sections for such applications.

Valve cover gaskets found on older Chrysler V8s, especially the Big Block family (361, 383, 400, 413, 440), face even more extreme temperatures. Due to underhood space constraints, some exhaust manifolds were designed with only a fraction of an inch clearance from the valve cover flanges. These gaskets can be subjected to temperatures as high as 700°F. No rubber or cork gasket could withstand this heat for extended periods, so Mangum offers special high temperature composite material containing Kevlar© and graphite.

Molded rubber, primarily silicone, gaskets are now the most frequent OE design. The days of the flat gasket "die cutter" are numbered. Successfully designing valve cover gaskets now requires years of experience and knowledge in molding die design and rubber compound processing. This is Magnum's strength.

When inferior molded gaskets (mostly imported) leak in service, it is often due to suffering from "compression set". That is measure as the percentage of how much the rubber compound relaxes due to time and temperature. For example, Magnum controls the manufacturing process, including post curing, so that compression set does not exceed 15-20%. Low cost molded gaskets from overseas, often suffer 40-60% or even higher compression set.

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