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    2JZ-GTE Head Studs (Toyota Supra Mark IV, Aristo, Soarer)

    2JZ-GTE Head Studs (Toyota Supra Mark IV, Aristo, Soarer), TorqBolt 12-point head stud with tB ligature and MP35N grade marking

    The Toyota 2JZ-GTE inline-six turbo (Mark IV Supra, Aristo VVTi, Soarer Twin Turbo) has a closed-deck iron block and aluminum cylinder head retained by 14 M12 head bolts in a 2-row-of-7 pattern. The closed-deck iron block tolerates extraordinary boost (the 2JZ is famously documented to handle 1000+ horsepower on the stock bottom end), but the stock TTY M12 head bolts are the limit. Boost above 25 psi on stock head bolts repeatedly lifts the head, even with a closed-deck block.

    TorqBolt 2JZ head studs (TB-2JZ-MP35N) ship as 14 M12 x 1.5 thread + matching 12-point nuts in MP35N (260 ksi) or Custom 465 H1025 (220 ksi). The MP35N alloy is preferred for the 2JZ because the long stud length (around 145 mm) means total elongation under preload is significant, and MP35N retains tensile strength reliably across the engine-temperature operating envelope.

    2JZ head stud install sequence

    1. Remove factory head bolts in REVERSE order. The factory TTY bolts are not reusable.
    2. Chase all 14 M12 x 1.5 threaded holes with a thread chaser.
    3. Install studs hand-tight then back off 1/2 turn so each stud free-floats in the iron block.
    4. Set head with new HKS or Cometic MLS gasket.
    5. Lubricate stud threads + under-nut washer face with TorqBolt moly assembly lube.
    6. Tighten in 3 stages following Toyota service manual pattern from center outward: stage 1 at 30 N-m, stage 2 at 60 N-m, stage 3 at 100 N-m final.
    7. For 1000+ hp drag-race builds: torque-angle method, turn each nut 90 degrees from stage 2.
    8. Re-torque after first heat cycle.

    2JZ alloy decision matrix

    For street + occasional drag (target 500 to 700 hp): heat-treated 8740 chromoly head studs are sufficient. For sustained 700 to 1000 hp street/strip: Custom 465 H1025. For 1000+ hp drag racing or roll-racing builds: MP35N. The 2JZ closed-deck iron block is the limit of what the bottom end can handle without girdle / deck plate; head stud upgrade alone keeps the head clamped.

    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.