Tom, My head was NA and when I put it on the flow bench it looked like the flow was almost cut in in half. I took the dividers out and moved more CFM by raising the port and reshaping the combustion chamber, and straighting the runners on the side. This was on a GMC head and when you open the intake ports you run into the head bolts and even with the tubes installed their is some port choke. I think in all we added almost 75-90 pounds of steel with the welder.
