ARP Header Bolts 8mm x 1.25 Thread, 1.181in Length — Set of 16 for Mopar Gen III Hemi, Chromoly Black Oxide with Washers

ARP Header Bolt, 8 mm x 1.25 thread and 1.181 inch length, is a premium chromoly hex-head fastener kit with washers engineered to secure headers on Mopar Gen III Hemi 5.7/6.1L engines.

This kit contains 16 bolts purpose-built for Chrysler Hemi header installations. Machined from 8740 chrome-moly alloy and finished in black oxide, each hex-head fastener is paired with the appropriate washer to ensure even clamping and corrosion resistance. Manufactured in the United States, these bolts are sized for the 8 mm by 1.25 thread pitch and have a 1.181 inch shank length, making them a direct-fit replacement for many Gen III Hemi applications.

Will these bolts fit my Mopar Gen III Hemi header?

These ARP fasteners are specified for Chrysler Hemi 5.7L and 6.1L header locations where an 8 mm x 1.25 thread and roughly 1.181 inch length are required. They were produced to match OEM-style header stud/bolt patterns commonly found on Gen III engines.

• Thread: 8 mm x 1.25 — matches standard Hemi header threads
• Length: 1.181 in — appropriate for typical header flange thickness plus gasket
• Set size: 16 bolts — covers both sides of many header configurations
• Includes washers — ensures proper load distribution and torque repeatability

How durable are these bolts under heat and vibration?

Made from ARP's 8740 chrome-moly (chromoly) alloy, these bolts offer high tensile strength and fatigue resistance compared with standard steel fasteners. The black oxide finish provides mild corrosion protection and reduces light surface reflection in engine bays.

• Material: 8740 chrome Moly — better strength under stress
• Finish: black oxide — reduces surface corrosion and improves appearance
• Washer included — minimizes flange damage and improves clamping
• Made in the USA — quality control and materials traceability

What tools and torque values should I use with these hex-head bolts?

Use a correctly sized socket or wrench to avoid rounding the hex head. Because these are chromoly fasteners, follow ARP or vehicle-specific torque recommendations and any supplied installation notes—typically a calibrated torque wrench and a proper torque sequence are required for header installation.

• Tool: hex socket or wrench matched to the bolt head
• Procedure: use calibrated torque wrench and follow sequence
• Safety: avoid over-torquing; chromoly bolts have specific torque/strain characteristics
• Tip: use anti-seize or lubricant only if manufacturer recommends it for your application

What comes in the box and are there any compatibility caveats?

The package supplies 16 hex-head bolts and matching washers, sized as described for direct header installations on many Mopar Gen III Hemi engines. Verify thread pitch, bolt length, and flange configuration before installation; some aftermarket headers or modified flanges may require different lengths or stud-style fasteners.

• Contents: 16 ARP bolts and washers — ready for one full header side or combined applications
• Compatibility: targets Chrysler Hemi 5.7/6.1L Gen III applications
• Limitations: confirm thread pitch and flange depth on aftermarket parts
• Installation note: studs vs bolts — this kit uses hex-head bolts, not studs

Who is this for: Experienced DIYers, professional mechanics, and performance shops replacing or upgrading header fasteners on Mopar Gen III Hemi 5.7L or 6.1L engines who want stronger, track-capable hardware. If you need direct-fit 8 mm x 1.25 header bolts with a 1.181 inch length, washers included, and premium 8740 chromoly construction finished in black oxide and made in the USA, this ARP set of 16 is designed to meet those needs.