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Automotive fasteners designed to secure exhaust manifolds and headers with factory-style fit and correct thread, Michigan Motorsports Exhaust Manifold Header Bolts. Peace of mind during installation comes from matching underhead length and torque specification for LS and LT V8 engines. Is this the reliable 12-piece set installers need for a worry-free exhaust fit?
⚡ At a Glance
- • Fitment & Compatibility: Fits 1997-newer LS and LT based GM V8 car and truck engines
- • Material & Strength: Flanged Grade 10.9 bolts for high tensile fastening
- • Thread & Length: M8 x 1.25 thread with 25mm underhead length
A 12-piece set of flanged Grade 10.9 bolts matched to M8 x 1.25 threads and 25mm underhead length. Torque spec for the M8 exhaust bolts is given as 18 ft-lb, and fitment covers 1997-newer LS and LT based GM V8 engines.
Reliable sealing and clamp load – thanks to M8 x 1.25 thread with 25mm underhead length
Correct underhead length ensures the bolt engages the flange and gasket area as intended, while the M8 x 1.25 thread matches factory and many aftermarket tapped holes. The flanged head increases bearing area under the bolt.
Consistent engagement reduces the risk of loose fasteners and exhaust leaks, which helps keep joints sealed under heat cycles. Installers can expect predictable clamp behaviour when matched with the correct torque.
High tensile fastening – with flanged Grade 10.9 bolts
Grade 10.9 denotes a high strength fastener class suitable for demanding automotive applications, and the flanged design removes the need for separate washers by widening the bearing surface. Torque guidance of 18 ft-lb is supplied for the M8 exhaust bolts.
Greater resistance to stretching and loosening under vibration improves long-term durability of exhaust connections. Using bolts rated to the appropriate class reduces the chance of breakage during repeated thermal expansion and tightening.
Straightforward compatibility across LS/LT families – thanks to explicit 1997-newer LS and LT fitment
Compatibility is specified for Gen 3, Gen 4 and Gen 5 LS and LT based GM V8 engines, indicating the fasteners match the common flange and thread standards used across those generations. The 12-piece count addresses typical manifold/header mounting points.
Mechanics working on a range of LS or LT engines can reuse the same fastener set without adapting thread sizes or lengths. The set simplifies repairs and swaps by matching the usual factory dimensions.
✨ The 4 Key Reasons for Michigan Motorsports Exhaust Manifold Header Bolts
- Flanged head – spreads load and reduces need for separate washers during installation
- 12-piece set – covers full manifold/header bolt patterns without sourcing extras
- Included torque spec – 18 ft-lb guidance for reliable clamp and repeatable tightening
- Designed for LS/LT generations – avoids sizing guesswork across Gen 3, 4 and 5 builds
📋 Technical Details at a Glance
- Category: Exhaust manifold/header bolts
- Quantity: 12 pieces
- Thread size: M8 x 1.25
- Underhead length: 25mm
- Grade: 10.9 (flanged)
❓ Frequently Asked Questions
Q: Will these bolts fit my 2005 LS1 engine?
A: Yes. Fitment is stated for 1997-newer LS and LT based GM V8 car and truck engines, which includes LS1-era vehicles.
Q: What torque should be used when installing these bolts?
A: Torque specification for the M8 exhaust bolts is given as 18 ft-lb, so follow that figure for consistent clamp load.
Q: Are the bolts suitable for aftermarket headers as well as factory manifolds?
A: Yes. The M8 x 1.25 thread and 25mm underhead length are specified to fit factory exhaust manifolds and aftermarket headers.
🏆 Our Verdict
Suitable for mechanics and home builders working on LS and LT V8 engines, the set supplies the correct thread size, underhead length and a clear torque recommendation. High-strength, flanged Grade 10.9 bolts reduce the likelihood of loosening and failure under thermal cycling. Expect long-term value from durable fasteners that reduce rework and retightening, especially on repeated installations.
