The Edelbrock 777869 SB2 Pro-Port Cylinder head is designed specifically for the professional cylinder head porter and engine builder. Like all other Edelbrock Cylinder heads, Pro-Port cylinder heads are also cast in the USA at the state-of-the-art Edelbrock Foundry with extra-thick walls to allow for custom CNC porting. In most cases, seats and manganese-bronze valve guides are included, but not installed. Please note: These heads can not be used without professional head preparation. Pro-Port RAW Features Include: - Unported versions of Edelbrock race-winning Victor Series CNC heads for the professional cylinder head porter and engine builder - Pro-Port cylinder heads are cast in the USA at the state-of-the-art Edelbrock Foundry with extra-thick walls to allow for custom CNC porting - The only heads designed specifically to accommodate almost any CNC port shape, size or location - Offers enough wall thickness for CNC machining to various port dimensions - In most cases seats and manganese-bronze - Some Edelbrock Pro-Port Raw Heads Feature Our Special Hot Isostatic Pressing or HIP Process.