ProMaxx heads have started a revolution in the performance world. They have custom designed a head to meet the demands of the Big Block Chevy world, while keeping the quality high and the price reasonable. These BB-Chevy heads come in an As-Cast series or Full CNC-Ported series. The As-Cast series features ''as-cast'' runners and combustion chambers with hand blended valve bowls. The Full CNC-series heads have professionally machined ports and combustion chambers that flow and perform as good as or better than some of the best cylinder heads in the industry. Basic components include U.S. made bronze valve guides, and ProMaxx 5-angle valve job. Assembled heads include 21-4N stainless valves, springs, retainers, 7/16'' rocker studs, guide plates, and viton seals (Bare heads do not include these items).