AFR 457cc Magnum BBC 18 degree cylinder heads were built specifically for high horsepower race applications. The Magnum 18 heads flow an impressive 498 cfm at 1.000 in. lift with 457cc runners, 90cc combustion chamber, and 143cc exhaust. The intake ports are raised .500 in. with the valves rolled to 18 degree, resulting in unparalleled under-the-curve flow numbers. These big block Chevy heads are ideal for 540 cu. in. or larger race engines. AFR has been defining what it means to make power on Chevy engines for years. Now you can strap on a pair of their best performing, highest flowing heads, their 457cc Magnum BBC 18 degree cylinder heads.