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    Mopar Hemi Head Studs (5.7L, 6.4L 392, 6.2L Hellcat, Demon)

    Mopar Hemi Head Studs (5.7L, 6.4L 392, 6.2L Hellcat, Demon), TorqBolt 12-point head stud with tB ligature and MP35N grade marking

    The Gen 3 Mopar Hemi family (Chrysler 5.7L, 6.1L SRT8, 6.4L 392, 6.2L Hellcat / Demon / Hellephant) shares a common iron block and aluminum cylinder head architecture. The head is retained by 10 M12 head bolts per bank (5 inner main + 5 outer secondary). Stock Hemi head bolts are torque-to-yield (TTY) and not reusable. The 6.2L Hellcat (706 hp factory) and Demon (840 hp) push the stock head bolts close to the limit even at factory boost.

    TorqBolt Hemi head studs (TB-HEMI-MP35N) replace the 20 stock M12 TTY bolts with 20 M12 studs in MP35N (260 ksi) or Custom 465 H1025 (220 ksi). The 12-point head on the stud nut clears the Hemi rocker-shaft pedestals where a hex socket would interfere.

    Hemi head stud installation

    1. Remove factory bolts in reverse pattern.
    2. Chase all 20 M12 holes per engine.
    3. Install studs hand-tight, back off 1/2 turn.
    4. Set head with new MLS gasket.
    5. Lubricate threads + under-nut face with moly lube.
    6. Tighten in 3 stages following Mopar pattern (center outward): stage 1 at 35 ft-lb, stage 2 at 65 ft-lb, stage 3 at 90 ft-lb.
    7. For 1000+ hp Hellephant / Demon-class builds: torque-angle stage 4 at 90 degrees.
    8. Re-torque after first heat cycle.

    Hemi family fitment

    All Gen 3 Hemi variants (5.7 Eagle, 6.1 SRT8, 6.4 392, 6.2 Hellcat, 6.2 Demon, 6.2 Hellephant 426) share the same head bolt pattern and accept the same TB-HEMI-MP35N stud kit. The 5.7 has slightly different rocker-shaft arrangement that affects valve cover clearance but does not change stud spec.

    Installation best practice

    Achieving the design preload is as much about the install method as the bolt: lubricant matters (published torque values assume 0.13 to 0.16 friction coefficient; anti-seize or moly-disulfide reduces friction 20 to 30 percent and over-stretches the bolt at the published torque). Direct bolt-stretch measurement with an ultrasonic gauge or stretch gauge over the bolt centerline cuts preload variation to under 5 percent vs torque-only at 25 percent. Race builders measure stretch.

    Re-torque after first heat cycle (run engine to operating temperature, allow to cool overnight, re-check torque) recovers preload lost to embedment at the faying surfaces. Conventional alloy-steel and MP35N bolts benefit from re-torque; torque-to-yield (TTY) bolts are NOT re-torqued and are typically replaced rather than reused after disassembly.

    Alloy choice vs build budget

    For street + occasional drag (target 500 to 700 hp): heat-treated AISI 8740 chromoly at 200 ksi is sufficient. For sustained 700 to 1000 hp street/strip: Custom 465 H1025 at 220 ksi or L19 race-grade at 270 ksi. For 1000+ hp drag racing or roll-racing: MP35N at 260 ksi. The bottom-end limits (rod tensile, main-cap stretch, deck flatness) become the bottleneck above this level, not the bolt.

    Frequently asked questions

    What is a 12-point bolt?

    A 12-point bolt has 12 splines arranged every 30 degrees on the OUTSIDE of the bolt head, also called a bi-hex or double-hex bolt. The 12 external splines provide twice the wrench-engagement angles of a standard hex head, allowing higher applied torque before cam-off, which is why aerospace and motorsport applications adopt the geometry.

    Are 12-point bolts the same as ISO 14579?

    No. ISO 14579 specifies an INTERNAL hexalobular socket head (similar to Torx) recessed inside a cap screw. External 12-point bolts under MS21250 / NAS1351 / AS3216 use an EXTERNAL bi-hex head driven by a 12-point socket wrench. Both involve 12 features but on different sides of the bolt head and require different drivers.

    Which alloys does TorqBolt manufacture 12-point bolts in?

    TorqBolt produces 12-point bolts in A286 (UNS S66286), Inconel 718 (UNS N07718), Ti-6Al-4V Grade 5, MP35N (UNS R30035), Custom 465 H1025, AISI 8740 chromoly heat-treated, AISI 4340, 17-4 PH, H-11 tool steel, and L19 race-grade alloy steel. Choice depends on tensile target, service temperature, and corrosion environment.

    Is TorqBolt AS9100D certified?

    Yes. TorqBolt operates under AS9100D Rev D and ISO 9001:2015 quality management systems, audited annually by the registrar. NORSOK M-630 and NACE MR0175 / ISO 15156 qualifications cover offshore and sour-service applications. Mill test reports MTC 3.1 standard and MTC 3.2 critical-service witness are issued with every lot.

    What lead time should I expect?

    Stock alloys (A286, AISI 8740, AISI 4340, 17-4 PH, 316 stainless) ship in 4 to 6 weeks. Specialty alloys (Inconel 718, MP35N, Custom 465, Ti-6Al-4V, L19) ship in 8 to 12 weeks depending on raw-bar lead time at the alloy producer. Critical-service orders requiring third-party witness inspection (MTC 3.2) add 1 to 2 weeks for witness scheduling.

    Request a Quote

    Send a build sheet (engine variant, target boost, fuel, gasket choice) and we will return a firm quote within 24 working hours. Email info@torqbolt.com, call +91-22-66157017, or WhatsApp wa.me/912266157017.