Unlock the hidden potential of your engine with powerful Top End upgrades from Zipper’s Performance Products. Zipper’s Performance keeps specially CNC-machined heads in stock for super-quick turnaround (on an exchange basis) for Milwaukee-Eight®, Twin Cam® and Sportster® engines. Big Bore conversion kits for Milwaukee-Eight®, Twin Cam® fitted with forged pistons in many different compression ratios for fast turnaround or exchange. Zipper’s Performance also stocks pistons, valves, guides, valve spring kits, and other critical top end parts from the industry’s most renowned manufacturers.
Increasing the size of a Milwaukee-Eight® engine is easy with Zipper’s Big Bore Cylinder Kits. These Big Bore kits are designed for the new Gen 2 M8 engines, which have oval port heads and center cooling.
The Milwaukee-Eight® engines design is made for displacement increases and Zippers offers cylinder kits for Factory stock 4-valve head, SE heads and many Custom High Flow Heads to provide huge torque and horsepower gains.
Each of this specific bore sizes are designed to fit on the factory engine base without case boring just like like-stock installation.
4.250- 4.280 Bores
Zipper’s offers new alloy castings with bore sizes from 4.250 to 4.280
These castings are designed with additional aluminum for added strength vs a O.E. casting with a larger bore liner with the following features:
• Cast Aluminum has 1 lb. additional material for Strength and Reliability
• Stress Relieved Iron Liners
• Precision Sized on Sunnen SV-30 by Zipper’s skilled craftsman
• Special Ring Packs for Advanced Cylinder Sealing
• Gasket Surface Finish Improved for Superior Seal using Cometic MLS Gaskets
• Zipper’s Forged “Spec Built” Pistons manufactured by CP
We have many dome configurations to choose from so you can target various compression ratios. Contact Zipper's support if you have a special requirement.
4.250 x 4.500 stroke = 128ci
Kits include precision fitted cylinders with tight tolerances, 2618 forged pistons with advanced ring packs, pins & clips, head and base gaskets and new head bolts. The rings custom sized to each cylinder.
Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.
***To ensure you enjoy a premium experience with a Zipper's Cylinder Kit, Please fill out a Job Order Sheet prior to completing an order on the website.
Click here for Zipper's Job Order Sheet
Please choose your application below then select the radio button next to the item to purchase, then add to cart
Increasing the size of a Milwaukee-Eight® engine is easy with Zipper’s Big Bore Cylinder Kits.
The Milwaukee-Eight® engines design is made for displacement increases and Zippers offers cylinder kits for Factory stock 4-valve head, SE heads and many Custom High Flow Heads to provide huge torque and horsepower gains.
Each of this specific bore sizes are designed to fit on the factory engine base without case boring just like like-stock installation.
4.250- 4.280 Bores
Zipper’s offers new alloy castings with bore sizes from 4.250 to 4.280
These castings are designed with additional aluminum for added strength vs a O.E. casting with a larger bore liner with the following features:
• Cast Aluminum has 1 lb. additional material for Strength and Reliability
• Stress Relieved Iron Liners
• Precision Sized on Sunnen SV-30 by Zipper’s skilled craftsman
• Special Ring Packs for Advanced Cylinder Sealing
• Gasket Surface Finish Improved for Superior Seal using Cometic MLS Gaskets
• Zipper’s Forged “Spec Built” Pistons manufactured by CP
We have many dome configurations to choose from so you can target various compression ratios. Contact Zipper's support if you have a special requirement.
4.250 x 4.375 stroke = 124ci
4.250 x 4.500 stroke = 128ci
Kits include precision fitted cylinders with tight tolerances, 2618 forged pistons with advanced ring packs, pins & clips, head and base gaskets and new head bolts. The rings custom sized to each cylinder.
Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.
***To ensure you enjoy a premium experience with a Zipper's Cylinder Kit, Please fill out a Job Order Sheet prior to completing an order on the website.
Click here for Zipper's Job Order Sheet
Please choose your application below then select the radio button next to the item to purchase, then add to cart
Turn your 107" M8 engine into a 117" by simply boring your stock cylinders! No case modifications necessary, the factory 107" can be safely bored from 3.937" to 4.125". These forged pistons are manufactured for us by CP-Carrillo in 3 different compression ratios (flat top compression ratio is 11.2:1 with an unmodified 87.5cc head) and feature 1.5mm compression rings with 3mm oil rings for superior oil control. Piston kits include pistons, rings, wrist pins and circlips. USA made!
Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.