Page 149 of GM Performance Parts 2006 Catalog by GM Parts Direct

ZZ4 Aluminum Cylinder Head Assembly (exhaust) ZZ4 Aluminum Cylinder Head Assembly (combustion chamber) ZZ4 Aluminum Cylinder Head Assembly (intake) 147 THE ZZ4 ALUMINUM HEAD The L98 Corvette small-block was a breakthrough in advanceddesign and efficiency largely because of the lightweight aluminum heads that were used on that engine. GM Performance Parts now offers you that same cylinder head in one complete assembly that features a D-shaped exhaust port 2, high-velocity intake runners, and centrally-located spark plugs 3. The applications are endless. 12556463 ZZ4 Aluminum Cylinder Head Assembly Aluminum performance head used on ZZ4 engines Completely assembled with 1.94"/1.50" valves 163 cc intake port 58 cc combustion chamber No heat riser Angled spark plugs (5/8" hex, 3/4" reach, tapered plugs) 1.48" Valve spring seat diameter Screw-in studs (3/8" top, 7/16" bottom) Use head gaskets with stainless steel fire rings Raised, machined rocker rails Exhaust ports are raised .100", requires Fel-pro gasket #1470 Use rail type rockers P/N 10089648, or kit P/N 12370838 (rollers!) This head is assembled with the following components: 12550909 Intake Valves 10212808 Valve Spring Retainers 10241743 Exhaust Valves 460483 Intake Valve Stem Seals 12551483 Valve Springs 10147883 Exhaust Valve Stem Seals 10212809 Valve Spring Shims 12564852 Valve Locks 12552126 3/8" Rocker Studs 2D-shaped exhaust ports increase the scavenging of the exhaust after combustion. The quicker you can get the exhaust out, the quicker you can get the air/fuel mixture into the combustion chamber. And, that equals big power! 3Centrally-located spark plugs allow for a more efficient flame front and air/fuel mixture burn during combustion, greatly increasing the power potential of the cylinder head.

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