S&S Cycle Cylinder Stud and Head Bolt Kit for 2017-2023 Harley-Davidson M8

S&S Cycle Cylinder Stud and Head Bolt Kit for 2017-2023 Harley-Davidson M8

Big bore conversions and high-compression builds demand fasteners that won’t stretch, back out, or fail under extreme cylinder pressures. This kit replaces both the cylinder studs and head bolts on Milwaukee-Eight engines with hardware engineered to handle the loads that performance builds generate – and it’s reusable, so it won’t add recurring cost to your next top-end service.

Key Features

• 8 chrome moly 4140 cylinder studs and 8 heat-treated 8640 head bolts in one complete kit
• Head bolts deliver 14 percent greater strength than stock with 200,000 psi ultimate tensile strength
• Cylinder studs oil-quenched and tempered to 39-44 HRC with 180,000 psi tensile strength
• Positive-stop shoulder on studs ensures consistent installed height across all installations
• Compatible with both MLS and graphite head gaskets – reusable head bolts

Technical Specifications

• Cylinder Studs: 4140 chrome moly, oil quenched and tempered, 39-44 HRC, 180,000 psi tensile strength
• Head Bolts: 8640 heat-treated steel, 200,000 psi ultimate tensile strength, 14% over stock
• Head Bolt Head: 9/16 inch 12-point with integral washer, black oxide coating
• Thread: Formed threads, cold-formed head
• Gasket Compatibility: MLS and graphite head gaskets
• Kit Quantity: 8 studs and 8 head bolts

Fitment Notes

• Fits 2017-2023 Harley-Davidson Milwaukee-Eight (M8) models
• Recommended for all big bore applications on M8 engines
• Head bolts are reusable – do not substitute with single-use OEM fasteners on performance builds
• Review the Fitment tab for complete year and model breakdown