Zipper’s Machining Services offers our blueprinting service for factory Twin Cam® cylinders that allows you to increase your engine size by simply replacing your stock cylinders and pistons with our specially modified units. We start with a seasoned set of factory cylinders. Once they are cleaned and inspected, the dowels are removed and the head gasket surface is precision machined for flatness and optimum gasket sealing surface. Then each cylinder is bored to the desired undersize before being fitted with torque plates and honed in stages on our Rottler CNC hone, precisely fitted to the hand-measured pistons chosen for the application.

We stock a wide selection of high quality forged pistons in several compression ratio configurations, and we verify with you that the components of your engine and the pistons chosen match the application for the optimum performance result. Each part number below also includes high quality top end and cam change gaskets (we can also custom-tailor your head gasket thickness if requested).

We stock cylinders fitted with pistons that are sold on an exchange basis to minimize turnaround time, or we can fit your supplied cores if requested. Just carefully pack up your stock, unmodified TC cylinders and send them to us. We can also sell you a set of factory cores outright at a very reasonable cost if you want to avoid any downtime (cores can be returned later for credit upon inspection). Any way you choose, you can count on our legendary attention to detail to make your Harley® the best it can be!

KITS FOR 1999-2006 TWIN CAM® ENGINES Factory 1999-2006 Twin Cam® engines are equipped with 4” stroke crankshafts. The factory cylinder bore size of 3-3/4” yields the 88” displacement. We can turn your 88” engine into either a 95 or a 98”, simply by resizing the factory cylinders.


This product is not for sale or use on pollution controlled vehicles.

Weight 1 lbs

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