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
Duramax Head Studs
Aftermarket 12-point head studs for the GM 6.6L Duramax V8 diesel engine, manufactured by TorqBolt in MP35N (260 ksi) and Custom 465 (220 ksi H950) alloys. Each stud cap face carries the struck tB ligature plus the alloy grade marking (MP35N or specified).
High-boost diesel rebuilds and work-truck performance upgrades commonly replace the factory head bolts with aftermarket head studs to handle higher peak cylinder pressures (often 200+ bar) without head-gasket lift. Head studs deliver more accurate clamping load than torque-to-yield head bolts and allow easy head removal between rebuilds.
Why head studs over factory head bolts
- More accurate clamping load (preload measured by stretch, not torque-yield)
- Easier head removal between rebuilds (head lifts off studs, studs stay in block)
- Higher tensile capability than factory torque-to-yield bolt material
- Reusable across multiple service cycles
Alloys
| Alloy | Tensile | Use case |
|---|---|---|
| MP35N (UNS R30035) | 260 ksi | extreme-boost performance |
| Custom 465 H950 | 220 ksi | standard high-performance |
| AISI 8740 chromoly HT | up to 220 ksi | cost-conscious upgrade |
Duramax head stud retrofit context
The GM 6.6L Duramax V8 diesel uses 18 M14 head bolts per engine in TTY configuration. The aluminum head bolts to an iron block, which makes head-gasket integrity sensitive to deck flatness and bolt clamp accuracy. Stock bolts handle factory 22 psi; 30+ psi tow or sled-pull builds need the upgrade. MP35N head studs at 260 ksi handle 60-80 psi.
Engine-Specific Installation Notes
Diesel head stud retrofits in high-boost applications (35 psi+ on Ford 6.0L Powerstroke, 50 psi+ on 6.7L Cummins, 30 psi+ on Duramax) require careful sequencing. Common practice:
- Remove factory head bolts in reverse of the factory torque sequence to avoid warping the head.
- Chase all threaded holes in the block and remove any debris with compressed air.
- Install studs hand-tight, then back off 1 turn so the stud free-floats during head installation. The head sets the stud position, not the operator.
- Install head and stud nuts. Lubricate threads and under-nut washer face with the manufacturer-specified lubricant (typically moly + oil mix).
- Tighten in 3 stages following the factory torque pattern: stage 1 to 30 ft-lb, stage 2 to 60 ft-lb, stage 3 to final torque (typically 110 to 130 ft-lb depending on engine).
- For higher-boost retrofits, manufacturer may specify a 4th step: turn the nuts an additional 90 degrees from final torque (torque-angle method).
- Re-torque after first heat cycle (run engine to operating temperature, allow to cool overnight, re-check torque) to recover any lost preload.
Always follow the bolt manufacturer's torque spec, not the factory bolt spec. Aftermarket studs in higher-strength alloys (MP35N at 260 ksi) take significantly higher final torque than factory bolts (8740 at 150 to 180 ksi).
Request a Quote
Specify GM 6.6L Duramax application + alloy preference + bolt circle measurement. RFQ to info@torqbolt.com, call +91-22-66157017.
Other diesel-truck head-stud platforms
TorqBolt produces aftermarket 12-point head studs in MP35N, Custom 465, and AISI 8740 chromoly for the most-rebuilt diesel-truck platforms. See the head studs parent page for the full bore-pattern, stud-length, and nut-thread fitment guide.
- Ford 6.0L Powerstroke, V8 turbo-diesel
- Dodge / Ram 6.7L Cummins, inline-six turbo-diesel
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