ZIPPERS Stage III M8 ThunderSport CNC Headwork

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. Zippers 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.

Cost $1,745.00

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• CNC Porting Improves Bowl & Short-Turn Flow
• Oversize 41mm Intake, 33mm Exhaust Valves
• 345 CFM Intake Port Flow
• 202 CFM Exhaust Port Flow
• Precision Valve Height Matching
• Competition Valve Job with De-Shrouding for Improved Flow
• Decking to Achieve 92.5cc Combustion Chamber
• Performance Valve Springs Set Up for Cam
• Custom decked for your specific application
• Best quality workmanship and materials used
• Supports140+HP/TQ On 4.125-4.250″ Bore Engines

Work is performed on your supplied head cores; shop time is approximately 10 business days (allow for additional time during peak season). Exchange heads may be available if the condition of your cores qualifies. 


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