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 a disassembly and inspection of the seats and valves. After the seat integrity inspection, factory guides are removed and replaced with long wearing manganese bronze guides and fitted with precision care.  The valves and seats are professionally multi-angle machined and port 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 is 89-90 cc.

• This service is available for Oil Cooled- Twin Cooled heads
• Additional valve or seat replacement may be required-quoted after inspection
• Optional 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 Performance Part Number:  517-852EX

 

DOCUMENTS & DOWNLOADS

Click here for Zipper’s Job Order Sheet

 

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.

Weight 20 lbs
Dimensions 10 × 10 × 10 in
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