Intake Manifold Gaskets

living in a tough environment

Intake Manifold Gasket Function
Every intake manifold gasket must seal a fuel-air mixture being drawn in the cylinders at a wide range of speeds and temperatures. So the initial requirements for these gaskets are fuel-resistance, conformability and not too much porosity of the material. Usually printed beads or embossments, for increased sealing stress, are required around ports to prevent vacuum leaks.

Sealing coolant flow between cylinder heads and intake manifold is another critical role for many intake gaskets. As we'll discuss below, the challenges to this task are much, much greater in recent years due to use of extended life anti-freeze and poor cooling system maintenance.

Finally, some engines also channel exhaust gasses through intake manifold gaskets for EGR and/or manifold pre-heating. This adds another major burden on intake gaskets; requiring them to seal, meter or block hot exhaust gas.

The overall category of "Intake Manifold Gaskets" also includes "Upper Manifold" or "Plenum" gaskets. These gaskets are required because the intake manifolds on many fuel-injected engines are split into an upper section (plenum) and lower section leading to the cylinder head(s). The Upper Manifold Gaskets seal the joint between the upper and lower manifold sections.

Intake Gasket Materials and Designs

The four principal constructions of intake manifold gaskets are:

On modern engines, use of paper gaskets without sealing beads are mostly limited to Upper (plenum) Manifold Gaskets. They have less exposure to heat and vibration than the lower gaskets, so paper can be cost effective and resist torque loss.

Also, high performance engine builders sometimes prefer paper intake manifold gaskets without steel cores. This is because they often wish to trim the gasket ports to precisely match the cylinder head ports.

Most often these gaskets use a steel reinforcement that is called a "tanged" or "perforated" core. Then either embossments or silk screened beads are added around ports to increase sealing stress and sealability. When properly designed and manufactured, these are still the most cost-effective construction for sturdier, conventional engines, especially prior to the mid '90's. The alternative steel core construction is to use paper laminated with adhesive to a flat steel core.

Most of Magnum's conventional intake manifold gaskets are called MaxPrint. Our preferred construction is a premium grade, high density facing material combined to a perforated steel core. Sealing beads are printed at critical locations and a silicone top coat creates optimum sealing and reduces sticking when removed.

In the 1990's, as electronic fuel injection systems became more sensitive and lightweight aluminum castings and plastic components became common, the need arose for more leak-resistant intake sealing than conventional gaskets could offer. The auto industry moved toward a design with rubber sealing beads molded onto a nylon composite carrier. These gaskets required a major step up in the sophistication of the design, tooling and manufacturing of intake manifold gaskets, requiring expertise in molding plastic as well as rubber.

This has been a specialty of Magnum's manufacturing facility since that time. In the Magnum Gasket line, this construction is referred to as Magnum MaxDry SS, denoting the "Super Sealing" ability of these gaskets. In this design, rubber sealing beads are squeezed and displaced, requiring a precisely calculated void for the rubber to fill.

This design solved many field problems and became the standard of the industry, still used for many Original Equipment intake manifold applications today. Although manufactured in various parts of the world, material quality and process control are the keys to success. Long term sealing with this design is highly dependent on resistance to "compressions set", so that the bead does not flatten out and lose its seal. Magnum's molded gaskets are made with high quality, post-cured rubber compounds to avoid this problem.

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