Head gasket
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| − | + | ==Overview== | |
| − | + | The '''cylinder head gasket''' provide the critical seal between the engine block and the [[cylinder head]]. They seal the combustion in the [[combustion chamber]]s and keep [[coolant]] contained to the cooling ports in the heads and block. | |
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Blown head gaskets can be caused by various engine problems, and can be detected with certain techniques. Left unfixed, a blown head gasket could cause severe engine damage. | Blown head gaskets can be caused by various engine problems, and can be detected with certain techniques. Left unfixed, a blown head gasket could cause severe engine damage. | ||
Various different types of head gaskets exist today, for different applications. Care must be taken in removal of the old gasket, selection of a new gasket and proper installation of the new gasket. | Various different types of head gaskets exist today, for different applications. Care must be taken in removal of the old gasket, selection of a new gasket and proper installation of the new gasket. | ||
| − | + | [[Image:Head gasket ford 298-302.jpg|thumb|left|220px|Head gasket Ford 289 - 302 CID]]<br style="clear:both"/> | |
==Head gasket basics== | ==Head gasket basics== | ||
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In MLS gaskets, multiple thin layers of cold-rolled steel are coated with a very thin layer of elastomeric material. The elastomer "micro-seals" the surface imperfections in the metal, and resists gases, oils, coolants, and high combustion temperatures. | In MLS gaskets, multiple thin layers of cold-rolled steel are coated with a very thin layer of elastomeric material. The elastomer "micro-seals" the surface imperfections in the metal, and resists gases, oils, coolants, and high combustion temperatures. | ||
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====Copper head gaskets==== | ====Copper head gaskets==== | ||
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==Head gasket sealants== | ==Head gasket sealants== | ||
Current technology OEM and racing head gaskets are designed to be used without additional sealant, however there are cases where head gasket sealants are required or helpful. Head gaskets sealants are specifically designed for the application; due to extremely high pressure within the combustion chamber which must be contained by the combustion seal, generic fluid sealants such as silicone should not be used for head gasket sealing. Unlike RTV silicone, head gasket sealants do not cure, they remain pliable indefinitely thereby allowing the head/gasket/block interface to achieve metal-to-metal contact under the compressive load of the tightened head bolts. Metal-to-metal contact insures a proper combustion seal. Conversely, curing sealants such as RTV silicone can form a 'rubber layer' upon which the head/gasket/block interface are separated allowing combustion pressure to eventually form a leak path to the coolant system or to the outside of the engine. Differential expansion rates of bi-metal engines are also accommodated by use of proper head gasket sealants which will not shear because they do not cure. | Current technology OEM and racing head gaskets are designed to be used without additional sealant, however there are cases where head gasket sealants are required or helpful. Head gaskets sealants are specifically designed for the application; due to extremely high pressure within the combustion chamber which must be contained by the combustion seal, generic fluid sealants such as silicone should not be used for head gasket sealing. Unlike RTV silicone, head gasket sealants do not cure, they remain pliable indefinitely thereby allowing the head/gasket/block interface to achieve metal-to-metal contact under the compressive load of the tightened head bolts. Metal-to-metal contact insures a proper combustion seal. Conversely, curing sealants such as RTV silicone can form a 'rubber layer' upon which the head/gasket/block interface are separated allowing combustion pressure to eventually form a leak path to the coolant system or to the outside of the engine. Differential expansion rates of bi-metal engines are also accommodated by use of proper head gasket sealants which will not shear because they do not cure. | ||
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===Standard copper head gaskets and sealant=== | ===Standard copper head gaskets and sealant=== | ||
Traditional flat copper head gaskets require the use of additional sealant for cooling and/or oil passage sealing. Similar to steel shim gaskets, traditional copper gaskets have no sealants applied. | Traditional flat copper head gaskets require the use of additional sealant for cooling and/or oil passage sealing. Similar to steel shim gaskets, traditional copper gaskets have no sealants applied. | ||
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===Specific head gasket sealant products=== | ===Specific head gasket sealant products=== | ||
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