LS Head Studs (LS1, LS3, LS6, LS7, LSX, LQ4, LQ9, 5.3, 6.0, 6.2)
The Chevrolet LS V8 family (LS1 1997, through LS7 2005, LSX block, the truck variants LQ4 / LQ9, and the modern LT-direct-injection branch) shares a common 4.40-inch bore-spacing architecture and a head-bolt pattern that uses ten M11 head bolts plus five M8 outer-row bolts per cylinder bank. Stock GM head bolts are torque-to-yield (TTY) at the 11mm pattern, designed for around 35 to 40 psi peak boost on the production turbo applications. Boost above 12 psi on a stock-bolt LS engine repeatedly lifts the head off the deck, blowing the head gasket; the fix is aftermarket head studs.
TorqBolt LS head studs replace the stock TTY bolts with M11 + M8 high-strength studs in MP35N (260 ksi tensile) or Custom 465 H1025 (220 ksi). The studs are threaded into the block deck dry, allowing the head to set its own position before the nuts are torqued. Final torque on the M11 nut is 100 to 110 ft-lb (lubricated, per TorqBolt spec sheet, NOT the stock factory torque value, which is for the lower-tensile factory bolt). The 12-point head on the stud nut allows precise torque application even in the tight clearance under the LS valve covers.
Fitment matrix across the LS family
The LS head bolt pattern is shared across most variants but the bolt count and length differ. TorqBolt LS head stud kits are configured per engine variant:
| Engine | Pattern | Stud count per bank | Stud kit p/n |
|---|---|---|---|
| LS1, LS6 (5.7L car) | 10 M11 + 5 M8 | 15 per bank, 30 total | TB-LS1-MP35N |
| LS2 (6.0L) | 10 M11 + 5 M8 | 15 per bank, 30 total | TB-LS2-MP35N |
| LS3, LS7 (6.2L / 7.0L) | 10 M11 + 5 M8 | 15 per bank, 30 total | TB-LS3-MP35N |
| LSX (aftermarket Chevrolet block) | 10 M11 + 5 M8 (extended) | 15 per bank, 30 total | TB-LSX-MP35N |
| LQ4, LQ9 (6.0L iron truck) | 10 M11 + 5 M8 | 15 per bank, 30 total | TB-LQ-MP35N |
| 4.8 / 5.3 / 6.0 (truck) | 10 M11 + 5 M8 | 15 per bank, 30 total | TB-LR-MP35N |
| LSA / LS9 (supercharged) | 10 M11 + 5 M8 | 15 per bank, 30 total | TB-LS9-MP35N |
LS head stud installation sequence
The LS head bolt torque pattern is documented in the GM service manual; key points for the aftermarket stud upgrade:
- Remove factory head bolts in REVERSE of the factory torque sequence to relieve clamp evenly. Factory bolts are TTY and not reusable.
- Chase all 15 threaded holes per bank with a 11mm and 8mm thread chaser. Compressed-air-blow chips and oil residue from each hole.
- Install studs hand-tight, then back off 1/2 turn so each stud free-floats in the deck. The head will pull each stud to its final position when torqued.
- Set head onto the deck with new MLS head gasket (recommended Cometic, GMP, or OEM-equivalent multi-layer-steel gasket; do NOT reuse factory composite gasket).
- Lubricate stud threads + under-nut washer face with TorqBolt-supplied moly assembly lube. Do NOT use anti-seize or thread sealant.
- Tighten in 3 stages following the GM 10-bolt LS pattern (inner to outer, criss-cross): stage 1 at 22 ft-lb, stage 2 at 50 ft-lb, stage 3 at 90 ft-lb final (M11). M8 outer-row bolts: 22 ft-lb final.
- For boost above 30 psi: torque-angle method instead of stage 3, turn each M11 nut an additional 90 degrees from stage 2 (50 ft-lb).
- Re-torque after first heat cycle (run engine to 200 deg F, allow to cool overnight, re-check each nut at 90 ft-lb or torque-angle).
MP35N vs Custom 465 vs heat-treated 8740
For LS head studs, the alloy choice tracks boost target:
| Alloy | Tensile | Boost target | Cost relative |
|---|---|---|---|
| AISI 8740 chromoly heat-treated 200 ksi | 200 ksi | up to 25 psi | 1.0x baseline |
| Custom 465 H1025 stainless | 220 ksi | up to 35 psi | 2.0x |
| MP35N (cold-work + age) | 260 ksi | up to 60 psi (typical limit) | 3.5x |
Above 60 psi boost the limiting factor stops being head stud strength and shifts to head gasket integrity, deck-face flatness, and connecting rod tensile capacity. MP35N head studs in this range are not the bottleneck.
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.