ARP Custom Age 625+ Head Stud Kit – 6.6L L5P Duramax
The ARP Custom Age 625+ Head Stud Kit (230-4302) is engineered for 2017–2025 Chevrolet and GMC 6.6L L5P Duramax diesel engines. Designed for demanding, high-cylinder-pressure applications, this premium head stud kit provides increased fastening strength and improved resistance to fatigue compared to conventional cylinder head fasteners.
Manufactured from ARP's proprietary Custom Age 625+ super-alloy, these studs offer a nominal tensile strength of 260,000 PSI, making them an excellent choice for performance engine builds where maintaining consistent cylinder head clamping force is critical.
Whether you're rebuilding an L5P Duramax or preparing an engine for increased boost and cylinder pressure, ARP Custom Age 625+ head studs provide additional strength and security for the cylinder head assembly.
Features & Benefits
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Custom Age 625+ Super-Alloy: Premium high-strength material with a nominal tensile strength of 260,000 PSI.
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Increased Clamping Strength: Designed to support cylinder head retention under elevated combustion pressures.
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Excellent Fatigue Resistance: Engineered to withstand repeated loading and demanding engine operating conditions.
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Precision Manufacturing: Centerless-ground studs with threads rolled after heat treatment to optimize fatigue strength.
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Corrosion Resistance: Custom Age 625+ material offers excellent resistance to atmospheric corrosion and oxidation.
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Reusable Stud Design: Unlike factory torque-to-yield head bolts, ARP studs are designed to be reusable when properly inspected and installed according to ARP specifications.
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12-Point Fasteners: Includes chrome-moly steel 12-point nuts and precision-ground washers for proper load distribution.
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Application-Specific Design: Engineered for the GM 6.6L L5P Duramax cylinder head configuration.
Kit Includes
- 36 M12 ARP Custom Age 625+ head studs
- 36 chrome-moly steel 12-point nuts
- 36 parallel-ground washers
- 12 M10 ARP 8740 chrome-moly intake valley bolts
- ARP Ultra-Torque fastener assembly lubricant
Vehicle Fitment
Fits the following vehicles equipped with the 6.6L L5P Duramax diesel engine:
- 2017–2025 Chevrolet Silverado 2500HD
- 2017–2025 Chevrolet Silverado 3500HD
- 2017–2025 GMC Sierra 2500HD
- 2017–2025 GMC Sierra 3500HD
Engine: GM 6.6L Duramax L5P
ARP Part Number: 230-4302
Installation Information
Proper installation is essential to achieving the intended clamping force and performance of ARP head studs. Follow the installation instructions provided by ARP for part number 230-4302, including the specified thread preparation, lubrication, torque sequence, and torque values.
ARP Ultra-Torque fastener assembly lubricant is included with the kit and must be applied to the specified surfaces according to the manufacturer's instructions.
Important: Always follow ARP's installation instructions rather than factory head bolt torque specifications. Cylinder head gaskets are sold separately.
Download ARP 230-4302 Installation Instructions (PDF)
Why Upgrade to ARP Custom Age 625+?
Factory torque-to-yield head bolts are designed around original engine operating requirements. When cylinder pressure increases beyond factory levels, additional cylinder head clamping strength can become important.
ARP Custom Age 625+ head studs provide a higher-strength fastening solution for performance-oriented L5P Duramax engines. Their material properties, precision manufacturing, and fatigue resistance make them well suited for builds where cylinder head sealing and fastening reliability are priorities.
For questions about selecting the correct head studs for your L5P Duramax, contact Industrial Injection at 800-955-0476.
