S&S Cycle 129" Power Package Big Bore Kit for M8

The S&S Cycle 129" Power Package Big Bore Kit is engineered to transform your 107" Harley-Davidson M8 engine into a formidable 129" powerhouse. This comprehensive bolt-on performance engine upgrade delivers a significant boost in displacement and power, all without the need for complex case machining.

Description

Experience an unparalleled boost in power and torque with the S&S Cycle 129" Power Package Big Bore Kit. Designed specifically for 107" Harley-Davidson M8 models, this high-performance engine upgrade increases your engine's displacement to a massive 129" with a substantial 4.32" bore and a robust 11.0:1 compression ratio, utilizing durable forged pistons. The kit is a true bolt-on solution, eliminating the need for costly and time-consuming case machining. At its core, the package includes an advanced S&S oil pump/cam plate, featuring a striking blue anodized finish and independent scavenge sections for both the flywheel cavity and cam chest, ensuring optimal oil circulation. Enhanced oil flow capacity on both the feed and scavenge sides, coupled with a magnet in the cam chest and debris screens, guarantees superior lubrication and engine longevity. Fine-tune your engine with the adjustable pressure relief valve, accessible even after installation. Complementing this, the kit provides S&S Quickee pushrods, premium tappets, and hard-anodized billet aluminum tappet cuffs. The included S&S 550 cams are specifically engineered for big bore applications, working in harmony with S&S valve springs capable of handling up to 0.605" lift, featuring a high-performance conical single wire spring design. This complete package ensures not just a power increase, but also enhanced reliability and precision engineering, all proudly made in the USA.

Features & Highlights

• Massive Displacement Increase: Transforms your 107" M8 engine into a potent 129" powerhouse, providing a significant boost in horsepower and torque without requiring any complex case machining.
• Optimized Power & Durability: Features 4.32" bore cylinders and high-strength 11.0:1 compression ratio forged pistons, engineered for extreme performance and long-term reliability.
• Advanced Oil System: Includes an S&S oil pump/cam plate with a striking blue anodized finish, independent scavenge sections, increased flow capacity, debris screens, and a cam chest magnet for superior lubrication and engine protection. An adjustable pressure relief valve allows for fine-tuning.
• Precision Valvetrain Components: Equipped with S&S Quickee pushrods, premium tappets, and hard-anodized billet aluminum tappet cuffs, ensuring precise valve timing and exceptional durability.
• Performance Cam & Valve Springs: Features S&S 550 cams optimized for big bore setups, paired with high-performance conical single wire valve springs capable of supporting cams up to 0.605" lift for aggressive power delivery.
• Complete Bolt-On Kit & USA Made: Comes with all necessary gaskets, bearings, and hardware for straightforward installation, proudly manufactured in the USA for superior quality and craftsmanship.

Technical Specifications

• Brand: S&S Cycle
• Product Type: Power Package Big Bore Kit
• Engine Compatibility: Harley-Davidson M8 (107" to 129")
• Displacement: 129"
• Bore Size: 4.32"
• Stroke Length: 4-3/8"
• Compression Ratio: 11.0:1
• Piston Type: Forged
• Cooling System: Oil Cooled
• Cam Drive Type: Gear
• Valve Lift Support: Up to 0.605"
• Cylinder Finish: Highlighted Fins, Wrinkle Black
• Oil Pump/Cam Plate Finish: Blue Anodized
• Pushrod Tube Color: Black
• Manufacturing: Made in the USA
• Vendor Part Number: 310-1227C
• MPN: 09040158

Important to Know

• Not for any Trike models.
• All necessary gaskets, bearings, and hardware for bolt-on installation are included.