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    Cylinder Head Bolts

    Cylinder Head Bolts, TorqBolt 12-point fastener with tB ligature and alloy grade marking

    Cylinder head bolts clamp the cylinder head to the engine block, gasketed against combustion peak pressure, and they have to hold that clamp through hot-cold thermal cycling without losing preload or pulling the threads. They are widely upgraded over OE bolts in heavy-duty diesel rebuilds, gasoline boost projects, and race builds because the stock TTY (torque-to-yield) bolts are not reusable and are sized for OE peak cylinder pressure, not the higher peak pressures that turbocharging, nitrous, or higher compression ratios produce. The 12-point head is very popular on cylinder head bolts because the head-bolt pocket is recessed deep into the head casting and the twelve splines allow higher applied torque without camming the wrench off the joint.

    TorqBolt manufactures cylinder head bolts in AISI 8740 chromoly heat-treated (220 ksi), AISI 4340, 17-4 PH H1025, Custom 465 and MP35N (for sour-service or marine duty) to AS9100D Rev D and ISO 9001:2015 quality systems. Each bolt head carries the struck tB manufacturer ligature plus the alloy grade marking, and every lot ships with a mill test report (MTC 3.1 standard, MTC 3.2 critical with hardness, tensile, magnetic-particle and rolled-thread-after-heat-treatment process records).

    Materials

    Alloy choice is set by the spec, the service temperature, the corrosion environment, and the strength target. TorqBolt routinely produces cylinder head bolts in A286 (UNS S66286), Inconel 718, Ti-6Al-4V (Grade 5), MP35N (UNS R30035), Custom 465 stainless, AISI 8740 chromoly heat-treated, AISI 4340, 17-4 PH H1025 condition, H-11 tool steel, and L19 race-grade alloy steel.

    Head bolts vs head studs

    Cylinder head bolts thread directly into the block deck and pull the head down with the bolt's own preload. Head studs are an alternate retention scheme: the stud threads into the block, then a 12-point nut on top of the stud sets the clamp. Studs allow the head to set its own position before the nut is torqued, which improves head-gasket seating accuracy on warped or high-mileage decks. For high-boost retrofits (35+ psi), studs are preferred. For OE-replacement and street-spec builds, bolts are sufficient.

    Request a Quote

    RFQ to info@torqbolt.com, call +91-22-66157017, or WhatsApp +91-22-66157017. Mill test report (MTC 3.1 standard, 3.2 critical-service) ships with every lot.

    Cylinder head bolts work in concert with other primary engine internals. See the related fastener pages for the engine context:

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