Page 147 of GM Performance Parts 2006 Catalog by GM Parts Direct

Bare Large Valve Cast Iron High-Performance Head (intake) C Bare Large Valve Cast Iron High-Performance Head (combustion chamber) C PERFORMANCE NON-VORTEC REPLACEMENT HEADS The legendary double hump or Camel Back cylinder head design was first introduced on the 1960 Corvette 283 V-8 and later used on high performance small-blocks, such as the 327 F.I. Corvette and 302 Z/28. GM Performance Parts has updated and improved it, and brought it back as a replacement head alternative. Performance Non-Vortec Head Technical Notes: Cast iron cylinder head 64 cc combustion chamber Straight spark plugs Heat risers Requires early model intake manifolds .530" Max valve lift Use P/N 12495497 studs for 3/8" rocker arms Use P/N 3921912 studs for 7/16" rocker arms Use P/N 3973418 guide plates for hardened pushrods Valve seats can be machined for 2.02" intake valves Valve spring seat diameter is 1.48" C. 12480092 Bare Large Valve Cast Iron High-Performance Head Machined for 2.02"/1.60" valves Completely bare, no studs or guide plates 88958692 Bare Cast Iron High Performance Leaded Fuel Head Machined for 1.94"/1.60 valves Non-heat-treated exhaust seats must use leaded fuel Completely bare, no studs or guide plates Same casting as P/N 12480092 THE PHASE 3 CAST IRON BOWTIE HEAD The Phase 3 Bowtie head was the first true cast iron performance head offered by GM Performance Parts. As such, it will outflow any production-style cast iron head. Intended for off-highway use only, the Phase 3 Bowtie head offers extra-thick castings for you to experiment with port modification. This head is designed for the all-out competitive racer who must run a production-style cast iron head. 12480034 Phase 3 Cast Iron Bowtie Head Cast iron Phase 3 Bowtie head Extra-thick walls for porting Machined for 2.02"/1.60" valves Exhaust seats are heat treated Valve spring seat is machined for 1.50" competition springs 184 cc intake runner 64 cc combustion chamber No heat riser Angled spark plugs (5/8" hex, 3/8" reach, tapered plugs) Requires early model intake manifolds Valve spring seat is machined for 1.50" competition springs Use P/N 12495497 screw-in studs for 3/8" rocker arms Use P/N 3921912 screw-in studs for 7/16" rocker arms Use P/N 3973418 guide plates for hardened pushrods Bare Large Valve Cast Iron High-Performance Head (exhaust) C 145

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