Page 209 of GM Performance Parts 2006 Catalog by GM Parts Direct

Bowtie Oval Port Aluminum Cylinder Head (exhaust) B Bowtie Oval Port Aluminum Cylinder Head (combustion chamber) B Bowtie Oval Port Aluminum Cylinder Head (intake) B 207 BOWTIE STREET HEADS GM Performance Parts is pleased to offer our Bowtie line of high performance street heads. They come with oval 1 or rectangular 2 intake port configuration, thick deck surfaces, and high velocity airflow passages. These heads also offer increased machining tolerances to live up to your high performance needs. With good throttle response and mid-range torque, the Bowtie line of big-block heads are perfect for street/strip big-block fans who want good low end grunt and loads of top end power. Bowtie Street Head Technical Notes: 356-T6 Aluminum 9/16" thick decks No heat risers Will work on Mark IV and Gen V VI cylinder blocks 1.55" Valve spring seat diameter Heli-coiled 7/16" screw-in rocker stud holes Designed for use with 3/8" pushrods Available as oval and rectangle ports As-cast intake and exhaust ports Use intake gasket P/N 12366985 bolt kit P/N 12367959 Use head gasket P/N 12363414 for bores to 4.37" P/N 12363413 for bores 4.47" to 4.54" (Mark IV) Use head gasket P/N 12363412 for bores to 4.37" P/N 12363411 for bores 4.47 to 4.54" (Gen V VI) Use Head bolt kit P/N 12367779 Oval Port Heads 12363399 Bowtie Oval Port Aluminum Cylinder Head (bare) Fully machined Bronze guides can be finished to 11/32" or 3/8" Semi-finished for 2.19"/1.88" valves 290 cc high-velocity oval intake ports 110 cc exhaust ports 110 cc semi-open combustion chambers B. 12363392 Bowtie Oval Port Aluminum Cylinder Head Assembly Completely assembled with 2.19"/1.88" valves 290 cc oval intake ports 110 cc exhaust ports 110 cc combustion chambers This head is assembled with the following components: 12366986 2.19 Intake Valves 12366990 Valve Spring Retainers 12366988 Exhaust valves 12366992 Valve Locks 12462970 Valve Springs 12495690 Valve Seals 3875916 Valve Spring Shims 3921912 Rocker Arm Studs 3860038 Pushrod Guideplates 12363390 Bowtie Oval Port Aluminum Cylinder Head Assembly Completely assembled with 2.25"/1.88" valves 290 cc oval intake ports 110 cc exhaust ports 110 cc combustion chambers This head is assembled with the following components: 12366987 2.25" Intake Valves 12366990 Valve Spring Retainers 12366988 Exhaust valves 12366992 Valve Locks 12462970 Valve Springs 12495690 Valve Seals 3875916 Valve Spring Shims 3921912 Rocker Arm Studs 3860038 Pushrod Guideplates 1Oval intake ports are smaller in volume and designed to enhance low rpm torque. They are an ideal street head for those big-block enthusiasts who want tons of bottom and power. 2Rectangular intake ports are larger in volume and designed to enhance high rpm horsepower. They are an ideal street head for those big-block enthusiasts who what more power from a street car that sees a lot of drag strip action.

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