S&S CYCLE 129" Power Package Engine Performance Kit — 129", 4.320" bore, 4.375" stroke, Black – 18-23 Softail, 17-23 Touring, 22-23 CVO

Upgrade your 107" oil-cooled M8 into a high-performance 129" engine without case machining required. 🚀

• Big bore cylinders come with matching cam, cam plate and oil pump for reliable power delivery.
• Independent scavenge sections for the flywheel cavity and the cam chest help maintain consistent oil control.
• A magnet in the cam chest helps prevent debris from entering the oil pump.
• High-performance conical single-wire S&S valve springs are included for improved valvetrain stability.
• Original engine serial numbers are retained and passage plugs are removable for servicing.
• Debris screens in both scavenge pickups and MLS (multi-layered steel) head gaskets ensure durability under load.
• Performance-matched 550 cam works with the stock crankcase for straightforward installation.
• Designed and manufactured in the USA.

This complete kit provides the components and engineering to upgrade displacement and breathing while keeping serviceability and reliability at the forefront.