S&S Cycle 310-1059D 124" M8 Power Package Big Bore Kit Gear Drive Oil Cooled

The S&S Cycle 310-1059D is a complete 124-cubic-inch Power Package big bore kit engineered for Milwaukee-Eight (M8) engines. This bolt-on kit upgrades displacement from 107 cubic inches to a full 124 cubic inches without requiring any case machining, making it an accessible and powerful performance upgrade.

At the heart of this package is a 4.250-inch bore cylinder set paired with forged pistons and an 11:1 compression ratio, delivering a significant increase in torque and horsepower over the stock configuration. The kit also includes an S&S high-performance oil pump and cam plate, precision machined from billet aluminum with a blue anodized finish.

Key Features:

• 107" to 124" big bore upgrade — no case machining required
• 4.250" bore cylinders with forged pistons
• 11:1 compression ratio for strong power output
• Gear drive cam system for precise, reliable cam timing
• Oil-cooled cylinder configuration
• S&S billet aluminum oil pump/cam plate with blue anodized finish
• Passage plugs are removable for easy servicing
• Independent scavenge sections for flywheel cavity and cam chest
• Debris screen in both scavenge pickups
• Magnet in cam chest helps prevent debris from entering the oil pump
• Increased oil flow capacity on both feed and scavenge sides
• Adjustable pressure relief valve — adjustable with unit installed in engine
• Made in the U.S.A.

S&S Cycle packages their proven 550G cam, cam plate, high-flow oil pump, valve springs, lifters, and pushrods together with the big bore cylinder kit for a comprehensive, single-purchase performance solution. The result is a reliable, street-ready engine build with substantially more displacement and power than the stock M8 platform.