If “Dirty Harry” drove a racecar, it would certainly be fitted with a pair of our 345 or 357 “Magnum” aluminum cylinder heads. If huge horsepower is what you are searching for, either of these castings will certainly deliver. With our Race Ready “As Cast” 345cc flirting with 400 CFM and our fully CNC ported 357cc flowing 425 CFM, these cyilnder heads represent the ultimate in airflow for your BB Chevrolet. Our 357 “Magnum” flows over 415 CFM @ .700 valve lift! No other production style BB Chevy head even comes close. Both of these cyilnder heads were targeted at larger cubic inch engines (509-632 CID) looking for maximum horsepower and rpm capability with a primary operating range of 3500-8000 rpm’s (This range is an average and will vary with engine displacement and component selection). As well, these aluminum heads provide impressive torque figures at higher rpm levels. Blown, turbo, and nitrous engines will especially like the larger, higher flowing intake ports. Both of these heads will work best with camshafts exceeding .750 gross valve lift to make better use of the substantial airflow found in the higher lift range. Both the 345cc and the 357cc come standard with AFR’s trademark .750” thick cylinder head deck, reinforced rocker stud bosses, and are equipped with premium one piece stainless steel 2.300” intake valves and 1.880” exhaust valves. Standard combustion chamber volume is 119cc’s on the 345 “As Cast” pieces, while our fully CNC ported 357 version comes with a 121cc chamber. Both are available with an optional 114cc combustion chamber as well. Note: Optional stud girdle required for 2° rolled valve angles and 1” longer head bolts needed on four bottom exhaust bolt holes. Chevrolet Big Block - 345cc Competition Package Ported Heads, Assembled - 119cc Combustion Chambers