Years of research and development have been invested to bring you the ultimate in bolt on performance for your Big Block Chevrolet. Airflow Research is proud to introduce our BB Chevy Aluminum cylinder heads. AFR's highly efficient port designs outflow the competition at every lift-point, even those with considerably larger runner volumes. An exclusive new combustion chamber design provides impressive swirl figures and help these heads generate big low and mid-lift airflow numbers. Considerable time has been spent to bring you a cylinder head which maximizes the entire flow curve, not just the big peak numbers. This aids in a much better ''cylinder fill'' and dramatically increases engine ''average'' airflow consumption (also spelled Horsepower!) The high velocity port designs help enhance engine acceleration as well as torque output. Structural features like our trademark 3/4'' head deck (a must for blown or nitrous engines), reinforced rocker stud bosses, and thick wall runners provide unparalleled durability, helping to create the strongest Big Block Chevy castings available today. Both intake and exhaust valve angles have been rolled two degrees to improve flow characteristics and provide a more efficient burn in the combustion chamber. The Unmatched Magnum version features combustion chambers with intake ports available at 305, 315, 325, 335, 345 and 357cc's. ''As Cast'' leaves the ports untouched or non-machined, so you can machine/tune your head the way that best fits your set up.