Transform 107" oil-cooled M8 into 129" with no case machining required. Big bore cylinders come with matching cam, cam plate and oil pump. Independent scavenge sections for flywheel cavity and cam chest. Magnet in cam chest to help prevent debris from entering oil pump. Feature high-performance conical single-wire S&S valve springs. Original engine serial numbers are retained. Passage plugs are removable for servicing. Debris screen in both scavenge pickups. MLS (multi-layered steel) head gaskets. Performance matched 550 cam. Works with stock crankcase. Made in the USA.