The cylinder head experts at Zipper’s offers the following premium selections carefully crafted for your engine builds.

M8 Engines

• M8 ST 1- Because there is so many problems with exhaust valve seat retention in a percentage of M8 castings, before installing big bore kits with the O.E. heads, Zippers offers a cleaning and inspection service to assure the valve seats are secure in the castings. We inspect the seal of the seats, install new valve seals and the heads are full assembled and ready to install.
• M8 ST 3- This is a fully developed CNC ported head with excellent flow that makes huge improvements to the inherently weak exhaust flow of the stock heads. Improved velocity to make excellent torque early. For use on big bore M8 engines. O.S. Valves are 41/33 mm. This head will make 140-155 HP in a variety of displacements with pump gas compression ratios using HPI Induction. Average combustion chamber size is 93.5 cc.

Standard Twin Cam Castings

• TC Stage 1.0- Your heads will receive our Stage I Performance Valve Job, 1.850” O.S. Valves, new guides and 7mm conical springs. The head gasket surface will be skim decked to assure a true/flat sealing surface. This is a high quality upgrade for a budget build! Combustion chambers are stock 85 to 86.5cc.
• TC Stage 2.0- Special high velocity port design with 1.900” O.S. Valves and 7mm conical springs. Designed for 88, 95, 98, 103, 107 or drop on 110 engines with aftermarket flat top pistons. Works great with stock TB and injectors at any desired compression ratio. The combustion chambers are 85 cc to 86.5 cc as cast.
• TC Stage 3.0– Larger higher flowing ports, 1.900” O.S. Valves and 5/16” dual spring that will handle up to .600” of cam lift. Full CNC chambers, ideal for higher output engines with dome pistons & larger Throttle Bodies. Can support engines up to 130 HP with excellent torque curves. Combustion Chambers are 91cc.
• TC Stage 3.5- A special high flow port that is the largest we can machine into an O.E castings.  Special O.S. 2.00” valves, special valve seats, 5/16” dual spring for lift up to .675”. The Stage 3.5 heads are max output models, and are a good option Vs purchasing CVO castings with the added expense of porting. Combustion chambers are 92 cc.
• TC Stage 4.0- The largest port we can machine into an O.E castings. O.S. 2.00” Valves, Special valve seats, 5/16” valve springs allow up to .750” of cam lift. Max flow design for big displacement engines with large airflow demand. Combustion Chambers are 98 cc and the large valves are un-shrouded.

CVO-MVA Castings

• CVO Stage 2.5- Fully CNC ported designed specifically to unleash great power in engines that require flat top pistons from 110-117 CI.  Combustion chambers are 95cc.
• CVO Stage 3.0– Our maximum flowing head upgrade for CVO castings. 2.100”/1.650” valves. Excellent port design, big valves, 5/16” dual springs for .660” of valve lift. Ideal for max output engines. Combustion chambers are 101 cc.
• MVA-120R- We offer custom head work for these castings.  Contact Zippers support with your specific needs.

Evo Head with OE Castings

• Ev Stage 1.0- Your heads will receive our Stage I Performance Valve Job, 1.850” O.S. Valves, new guides and 7mm conical springs. The head gasket surface will be skim decked to assure a true/flat sealing surface. This is a high quality upgrade for a budget build! Combustion chambers are stock 78 to 83cc.
• Ev ST 2– Special high velocity port design with 1.900” O.S. Valves and 7mm conical springs. Designed for engines with factory or aftermarket flat top pistons. The combustion chambers are 78 cc to 83 cc as cast.
• Ev ST 3– A special port design to promote high torque and high horsepower with 1.900” O.S. Valves and 5/16” dual spring that will handle up to .630” of cam lift. Full CNC chambers, ideal for higher output engines with dome pistons. The heads will be decked to achieve your desired compression ratio. Combustion Chambers are 86 cc before decking.

XL Sportster Castings

• We have multiple head packages that we can supply for the 5 Speed Sportster and Buell family of engines. Please contact one of our Representatives and we will be happy to discuss the options available to you.

Zipper’s has custom pistons with special domes and ring packs designed to work with most all of these castings plus a wide variety of Red Shift Cams for specific power applications.

If required our engineering department will gladly assist with each specific build from your shop plus custom decking and specific cc volume measurements are available for all heads to help you achieve your compression target of each specific build.

Contact us any time at productsupport@zippersperformance.com.

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