The complexity of the cylinder head gasket has largely been a result of the sophistication of modern engine designs. The cylinder head gasket is the most crucial sealing component on any engine. It must simultaneously seal high combustion pressures and temperatures as well as coolants and lubricating oil. The head gasket, along with the head, block, pistons and rings forms the combustion chamber. Meaning the cylinder head gasket must share the same strength requirements as these components. The head gasket is also used to meter or block coolant flow for proper cooling of the engine. It is therefore not uncommon for some water galleries to be blocked off by the head gasket. The three main materials used in head gasket manufacture today include:
- Includes a steel core with fibre facing material either side
- Steel core can be either perforated or tanged
- Fibre material usually has a chemical surface coating
- An elastomeric bead may be applied to the facing material to improve sealing by giving higher unit loadings where required
- Excellent surface conformability, oil and coolant resistance, and higher tensile strength than graphite
- Same construction as composite – graphite composite facing material either side of a steel core
- Excellent heat transfer capability, surface conformability and minimal relaxation at engine operating temperature.
Multi-Layered Steel (MLS)
- Most common construction used in modern engines.
- Consists of multiple steel layers – functional layers (outer layers) are usually coated with at least one coating between any two metals.
- The inner core (stopper-layer) applies a downward load down the bore walls and seals the combustion chamber.
- MLS gaskets require tighter surface finishes and distortions in the head and block than composite or graphite gaskets