The Vortec heads with the desirable flow numbers can easily be identified. ON ALL "good" Vortec heads, the intake manifold has EIGHT bolts. There are two bolts at each end of each head (four per head and eight per motor). These bolts are 5/16 dia and are VERTICAL (not slanted like the old small block chevy). Since there are no water transfer passages in Vortec heads, there are NO bolts in the center area of the manifold. And, by the way, ALL Vortec heads came with Vortec injection....there was never a carbureted Vortec head motor and never a tbi Vortec head motor.

The casting identifier at the end of the head is a saw tooth pattern on top of the rectangle.....it's easier to just look for the four intake bolts on each head however.

mike in tucson