Made just for use with the 12 Valve DIY kit, now you or your fabricator can make a fully custom intake manifold. Notice the center of each port is not directly inline with the port on the head. This was on purpose to make the same centerline port to port like the 24 valve engines. Center to center measurements are all the same now to help create an equal air flow to each valve. O-Ring Grooves cut for gasket seal, O-rings supplied also.