I am pretty sure this was covered in another thread but I do not recall which one. Check them out in the links of the thread below. If I remember correctly, the throat of the CNC small block Speedmaster heads was larger than it should be for the 2.02" intake valve they come with, and not shaped for optimal performance either. The best route is probably to have a real shop work up a set of bare heads to suit the intended use, starting with non-ported bare castings.
