Fastener torque
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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. | ||
| + | |||
| + | 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. | ||
| + | |||
| + | 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 | ||
| + | |||
| + | 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. | ||
| + | |||
| + | {{Note1}} Do not use RTV or any type of sealant or adhesive that hardens or sets up. The sealant needs to remain pliable, not hardened or brittle. | ||
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| + | ===Head gasket re-torquing=== | ||
| + | The purpose of re-torquing the cylinder head fasteners is to restore the proper stretch to the head bolts after the first heat cycle. The idea behind this is that the engine assembly will expand as the engine temperature increases, this expansion will increase the compressive load on the head gaskets, causing a seating effect (sometimes referred to as creep relaxation) in composite head gaskets. | ||
| + | |||
| + | The seating of the gaskets and threads results in a commensurate relaxation of the fasteners when the engine cools. Re-torquing the fasteners restores the proper stretch to the fasteners which will insure proper cold sealing of the gaskets as well as proper combustion sealing under full load. | ||
| + | *One re-torque is all that is necessary (unless the manufacturers instructions indicate otherwise) | ||
| + | *If your engine uses torque-to-yield head bolts (TTY), do not re-torque | ||
| + | *If there's any doubt, ask the manufacturer for a recommendation | ||
| + | |||
| + | ====The process for re-torquing is as follows:==== | ||
| + | *Start the engine and run with no load until operating temperature is reached | ||
| + | *Shut down the engine and let cool completely | ||
| + | *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). Whether or not this is done when using iron castings (research this beforehand) is up to the builder. But this should NOT be done with aluminum blocks or heads. | ||
==SBC and BBC== | ==SBC and BBC== | ||
[[File:Chevyv8 fastener torque.jpg]] | [[File:Chevyv8 fastener torque.jpg]] | ||
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==Resources== | ==Resources== | ||
*[http://www.crankshaftcoalition.com/wiki/Category:Fasteners Fasteners] | *[http://www.crankshaftcoalition.com/wiki/Category:Fasteners Fasteners] | ||
| − | * | + | *[http://www.derose.net/steve/resources/engtables/bolts.html Torque values of standard bolts, 1/4" and larger.] |
| + | *[http://euler9.tripod.com/bolt-database/ Metric and USA Standard Bolt Properties, Grades, and Strength], including: | ||
| + | :*Standard USA Bolt Shank Dimensions | ||
| + | :*Standard USA Bolt Hex Head and Hex Nut Dimensions | ||
| + | :*Typical USA Flat Washer Dimensions | ||
| + | :*Standard USA Hex Socket Outside Diameters | ||
[[Category:Engine]] | [[Category:Engine]] | ||
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