For the ultimate street LS1/LS2/LS6 aluminum cylinder head AFRÍs all new 205cc emission legal cylinder heads E/O # D250-4 are your only choice. Specifically designed for 1997 to present Gen-3 Chevy Corvettes, Camaros, and trucks. AFRÍs LS1 head offers unmatched flow performance (298 CFM at .600lift) and features 2.020 intake and 1.600 exhaust valves with AFRÍs iron ductile interlocking valve seats. With only 205cc port volume (same as stock LS1 head) this is an incredibly 70 CFM increase over stock casting creating unbelievable port velocity and performance. The 205cc is ideal for normally aspirated 346C.I. to 396C.I. It is available with 66cc and 76cc combustion chambers. AFRÍs LS1 is a direct bolt on, no special parts required. Structural features like Air Flow ResearchÍs trademark 3/4î thick head deck, a must for blown and nitrous applications, reinforced rocker stud bosses, and thick wall runners provide unparalleled durability. An exclusive new modern combustion chamber design with double quench pad area helps the LS1 generate huge low and mid lift airflow numbers. If you need a snake charmer for that pesky neighborhood ñCobra Mustangî look no further. Chevrolet LS1 - 205cc CNC Street Ported Heads - 66cc Combustion Chambers - Fully Assembled