Want to wake up the Big Block in your favorite tow vehicle? AFR's 265cc high-velocity oval port is just the ticket! They are also ideal on smaller cubic inch street performance applications (396-468 cid), providing "gobs" of bottom end torque, tremendous throttle response, and great all around power. With AFR's trademark 3/4" deck, reinforced rocker stud bosses, and thick rugged castings, you can own the strongest and most efficient heads on the market today. Premium hardware such as 2.190/1/880 one piece stainless valves, 1.550 double springs, 10 degree locks and retainers, and high quality studs and guide plates all come as standard equipment. Take note the higher flowing exhaust ports are raised .375 over stock location, and therefore these heads might not be a direct bolt-on in every application. These heads have no EGR and are not emissions legal. Note: Optional stud girdle required for 2Á rolled valve angles and 1" longer head bolts needed on four bottom exhaust bolt holes. Chevrolet Big Block - 265cc Competition Package Ported Heads, Bare - 121cc Combustion Chambers