ZIPPERS PERFORMANCE THUNDERSPORT CYLINDER HEADS HARLEY M8

ZIPPERS PERFORMANCE THUNDERSPORT CYLINDER HEADS HARLEY M8 

SELECT LEVEL OF HEADWORK IN OPTIONS 

THESE ARE AN EXCHANGE ITEM 

STAGE 2 -head upgrade begins with an inspection of the seats, guides and valves. After the seat integrity inspection is completed the valves and seats are professionally machined and blended to provide maximum flow in an un-ported head to achieve power and concentricity without the cost of ported heads. This process offers superior flow and sealing over the OE or a SE head. Heads are decked and fully assembled, ready for installation. Before decking approximate cc volume 89-90 cc

STAGE 3 -The 4-valve M8 cylinder head flows considerably more air than previous 2-valve heads – but it needs to, to support today’s larger engines. Flow testing the stock heads shows an imbalance between intake and exhaust flow ratios. Our combination of qualifying seat installation, CNC porting, professional seat and guide finishing with oversize valves, careful spring set up and decking ensures you will extract maximum power from your engine modifications while improving the flow imbalance. This work is performed on your supplied head cores.

STAGE 3.1-Similar to the STAGE 3 head, this fully developed CNC ported head has excellent flow that makes huge improvements required for large displacement M8 engines. This design has improved velocity helps make excellent early torque and peak HP.

STAGE 4-

This is Zipper’s newest fully developed CNC ported head designed for larger output engines. This head has large increases in flow over the STAGE 3 and tightens the spread between Intake to Exhaust flow ratio with significant improvements to the exhaust port design.

Only for use on big bore M8 engines. O.S. Valves are + 2mm 42/34 intake / exhaust valves.  Requires oversized Induction. Final combustion chamber cc range 89-90 cc.

• This service is available for Oil Cooled- Twin Cooled heads
• Porting performed with guides removed
• Included are Upgraded Valve Springs and New Guides
• Oversize valve seat replacement is required with 4.0