S&S Cycle 07-17 BT 107in Bolt-In Big Bore Kit - Wrinkle BlackThis bolt in big bore kit is easy to install, and requires no machining or rebalancing. This is the largest bore (3. 937") that can be fit in a stock engine case. Stock engine height is maintained so there are no manifold or frame fitment issues. The S&S 11 fin cylinder design closely resembles OEM shape and come prefinished ready to install. Cylinders feature increased fin area for better heat dissipation, and the centrifugal cast, gray iron liner