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 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

• This service is available for Oil Cooled- Twin Cooled heads
• Additional guides, valve or seat replacement may be required-quoted after inspection
• Upgraded valve springs available for larger lift cams

Work is performed on your supplied head cores. Once heads are received at Zipper’s, Shop Time is approximately 15 business days (during peak season allow for additional time). Exchange heads may be available if the condition of your cores qualifies. Currently we do not offer M8 cores for sale. Please send your cores in for processing or exchange.

International Customers – Import duties are not required when shipping your castings for modification. Special low shipping rates are available for your cores; contact your sales representative for details.

Remove heads from engine, wash off oil and ship to Zipper’s as-is. Improper cleaning methods can actually do more harm than good; we suggest you allow us to properly prepare your heads for modification. Extreme care is taken during our preparation process to preserve component finishes.



Zipper’s Engine & Powertrain Service Request


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

Weight 1 lbs

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