Standards
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
2JZ-GTE Head Studs (Toyota Supra Mark IV, Aristo, Soarer)
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
- Remove factory head bolts in REVERSE order. The factory TTY bolts are not reusable.
- Chase all 14 M12 x 1.5 threaded holes with a thread chaser.
- Install studs hand-tight then back off 1/2 turn so each stud free-floats in the iron block.
- Set head with new HKS or Cometic MLS gasket.
- Lubricate stud threads + under-nut washer face with TorqBolt moly assembly lube.
- 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.
- For 1000+ hp drag-race builds: torque-angle method, turn each nut 90 degrees from stage 2.
- 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.
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.
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