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
Mopar Hemi Head Studs (5.7L, 6.4L 392, 6.2L Hellcat, Demon)
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
- Remove factory bolts in reverse pattern.
- Chase all 20 M12 holes per engine.
- Install studs hand-tight, back off 1/2 turn.
- Set head with new MLS gasket.
- Lubricate threads + under-nut face with moly lube.
- 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.
- For 1000+ hp Hellephant / Demon-class builds: torque-angle stage 4 at 90 degrees.
- 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.
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.
Satisfaction Survey
