GM Performance Cylinder Head, LS9, Assembled, CNC-Ported, 66.5cc Combustion Chamber, Aluminum, Natural Finish, 2.16 in. Intake Valve, Each (PART #GMP-19433498)

GM Performance LS9 CNC-ported cylinder heads represent a new benchmark in factory engineering high performance, blending the strength and durability of the production LS9 cylinder head castings with the airflow enhancements of precision CNC porting. The result is about 10 percent more efficiency than the production casting, while delivering the greater strength built into the LS9--Rotocast from super-strong A356T6 aluminum alloy. With the Rotocasting method, the mold rotates to more evenly distribute the molten alloy, creating a denser casting that virtually eliminates porosity. And compared to the similar LS3 heads, GM Performance LS9 CNC-ported cylinder heads feature reinforced webbing and a thicker deck for greater rigidity and minimal distortion. The A356T6 alloy also manages the higher heat of a forced engine more effectively. The heads come fully assembled with production, lightweight titanium intake valves, sodium-filled exhaust valves, and strong beehive-type valve springs that can handle up to .570 in. lift and can be installed on any LS engine with at least a 4.000 in. bore using standard 11mm head bolts.