Head gasket
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| − | + | , and can be detected with certain techniques. Left unfixed, a blown head gasket could cause severe engine damage. Many symptoms of a bad head gasket are not apparent until the problem is very bad, including the ones listed later in this article. | |
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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. | ||
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====Graphite head gasket==== | ====Graphite head gasket==== | ||
| − | Graphite head gaskets can be used on aluminum heads with an iron block (they work equally well with iron heads on an iron block). Graphite is excellent in handling high temperatures and is anisotropic (draws heat away from hot spots). It also seals very well too. Some drawbacks to using graphite is that it cannot withstand exposure to oil | + | Graphite head gaskets can be used on aluminum heads with an iron block (they work equally well with iron heads on an iron block). Graphite is excellent in handling high temperatures and is anisotropic (draws heat away from hot spots). It also seals very well too. Some drawbacks to using graphite is that it cannot withstand exposure to oil over a long period of time, can be crushed and extruded, and it also leaves a coating on the block and heads that is harder to remove than traditional head gaskets. |
An article that mentions graphite gasket technology is '''[http://www.enginebuildermag.com/Article/2585/gasket_technology_the_science_of_sealing.aspx here]'''. | An article that mentions graphite gasket technology is '''[http://www.enginebuildermag.com/Article/2585/gasket_technology_the_science_of_sealing.aspx here]'''. | ||
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Any "leak stopper" or head gasket "repair additive" should be avoided. Use of such products leads to further engine damage, such as seized or leaking water pumps, clogged water or oil passages, or clogged radiators and thermostats. If you use these products, be aware of possible problems caused by them. | Any "leak stopper" or head gasket "repair additive" should be avoided. Use of such products leads to further engine damage, such as seized or leaking water pumps, clogged water or oil passages, or clogged radiators and thermostats. If you use these products, be aware of possible problems caused by them. | ||
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| + | ==Head gasket torquing== | ||
| + | Follow the sequence for the engine being worked on. If no sequence can be found, start from the inner fasteners and work outward. | ||
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| + | Use at least three steps, i.e. if the torque is 65 ft/lb, torque the first step to 20 ft/lb, second step to 40 ft/lb and the last step to 65 ft/lb. | ||
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| + | [[File:80632permatex.jpg|right]] | ||
| + | If using OEM fasteners, most times the recommendation is for the clean threads to be lubricated with motor oil before torquing. Threaded holes can be cleaned with a thread chaser. Do not use a tap for this, it can enlarge the hole and/or thin the threads by removing metal, increasing the chance of pulling the threads. | ||
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| + | Fasteners that enter the cooling jackets have to be sealed. Various sealants can be used depending on personal preference. Some sealers are: | ||
| + | *Hylomar | ||
| + | *Permatex #2 | ||
| + | *Permatex High Temp Thread Sealant | ||
| + | *Permatex High Performance Thread Sealant 56521 | ||
| + | *Permatex 80632 with teflon | ||
| + | *[http://www.summitracing.com/parts/ARP-100-9904/ ARP thread sealer] | ||
| + | *Locktite thread sealant | ||
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| + | Follow the factory torque specs unless aftermarket fasteners are used. In that case, follow the fastener manufacturer's directions for what type of lube to use and what torque to use- this will often differ from the factory specs. | ||
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| + | {{Note1}} Do not use RTV or any type of sealant or adhesive that hardens or sets up. The sealant needs to be pliant, not hardened or brittle. | ||
===Head gasket re-torquing=== | ===Head gasket re-torquing=== | ||
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*Retracing the original torque pattern one fastener at a time, slightly loosen the bolt or nut (to overcome the friction set), then re-torque to the specified torque setting | *Retracing the original torque pattern one fastener at a time, slightly loosen the bolt or nut (to overcome the friction set), then re-torque to the specified torque setting | ||
| − | It is suggested by some to retorque cast iron heads/blocks while still warm (not hot). | + | {{!}}It is suggested by some to retorque cast iron heads/blocks while still warm (not hot). Whether or not to do this when using iron castings is up to the builder (''research this beforehand''). But this should NOT be done with aluminum blocks or heads. |
===When replacing a blown head gasket=== | ===When replacing a blown head gasket=== | ||
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===SBC head gaskets having less than 0.040" compressed thickness=== | ===SBC head gaskets having less than 0.040" compressed thickness=== | ||
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*GM p/n 3830711 is also a steel shim with a 4.1" gasket bore diameter, and is 0.026" thick. Good flat surfaces are required, same rules apply as the Fel-Pro above. This is the GM production gasket for '''non''' 400 bore SBCs. Simple and low cost. | *GM p/n 3830711 is also a steel shim with a 4.1" gasket bore diameter, and is 0.026" thick. Good flat surfaces are required, same rules apply as the Fel-Pro above. This is the GM production gasket for '''non''' 400 bore SBCs. Simple and low cost. | ||
*GM p/n 10105117, this head gasket is a multi-layered stainless steel gasket with a 4.1" gasket bore diameter, is 0.028" thick, works with iron or aluminum heads, good for holding back high compression, and tolerates some surface irregularities in the deck and head surfaces. This is the “revised” gasket, see [http://www.thirdgen.org/techboard/tech-general-engine/269378-head-gasket-thickness-gm.html post #23]. | *GM p/n 10105117, this head gasket is a multi-layered stainless steel gasket with a 4.1" gasket bore diameter, is 0.028" thick, works with iron or aluminum heads, good for holding back high compression, and tolerates some surface irregularities in the deck and head surfaces. This is the “revised” gasket, see [http://www.thirdgen.org/techboard/tech-general-engine/269378-head-gasket-thickness-gm.html post #23]. | ||
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===Shim type=== | ===Shim type=== | ||
| − | * | + | *FelPro's p/n Q1094 is a steel shim with a 4.1" gasket bore diameter and 0.015" compressed thickness. Used in some sportsman drag race and flat top oval track categories. Rubber coated steel shim, 4.100 in. gasket bore diameter, 0.015" compressed thickness. |
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*SCE #511101 Specialty Component Engineering | *SCE #511101 Specialty Component Engineering | ||
**Bore: 4.100" | **Bore: 4.100" | ||
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**Lock Wire: No | **Lock Wire: No | ||
**Coolant sealing '''not''' compatible with GM lightweight head castings used on 305-350 from 1987-95. | **Coolant sealing '''not''' compatible with GM lightweight head castings used on 305-350 from 1987-95. | ||
| + | *Mr. Gasket p/n 1130 0.018”- 0.020” compressed thickness, steel embossed w/coating. | ||
| + | *Jegs p/n 210044- embossed shim w/rubber coating. Bore 4.150", compressed thickness is 0.024". | ||
===400 SBC=== | ===400 SBC=== | ||
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==References== | ==References== | ||
===Compression calculators=== | ===Compression calculators=== | ||
| + | ====Static CR==== | ||
*[http://www.wheelspin.net/calc/calc2.html Static compression ratio] | *[http://www.wheelspin.net/calc/calc2.html Static compression ratio] | ||
| − | *[http://www.empirenet.com/pkelley2/DynamicCR.html | + | |
| − | *[http://www. | + | ====Dynamic CR==== |
| + | *[http://www.wallaceracing.com/dynamic-cr.php Wallace Racing DCR calculator] | ||
| + | *[http://www.empirenet.com/pkelley2/DynamicCR.html Kelly DCR calculator] | ||
| + | *[http://www.uempistons.com/calc.php?action=comp2 KB/Silvolite DCR calculator] | ||
| + | *[http://www.rbracing-rsr.com/comprAdvHD.htm RSR DCR calculator] | ||
| + | {{Note1}} Some dynamic compression rtatio calculators (like KBs) ask for an additional 15 degrees of duration be added to the IVC @ 0.050" lift point figure. This works OK on older, slower ramped cam lobes, but the faster lobe profiles may need to have 25 degrees or more added to be accurate. | ||
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| + | {{Note1}}If the intake valve closing (IVC) point isn't known, it can be calculated: | ||
| + | # Divide the intake duration by 2 | ||
| + | # Add the results to the lobe separation angle (LSA) | ||
| + | # Subtract any ground-in advance | ||
| + | # Subtract 180 | ||
| + | This result does not need to have any amount added to the IVC point, like the KB calculator calls for. | ||
===Forum discussions=== | ===Forum discussions=== | ||
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[[Category:Engine]] | [[Category:Engine]] | ||
[[Category:Good articles]] | [[Category:Good articles]] | ||
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[[Category:Cylinder head]] | [[Category:Cylinder head]] | ||
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