If ñDirty Harryî drove a racecar, it would certainly be fitted with a pair of our 345 or 357 ñMagnumî aluminum cylinder heads. If huge horsepower is what you are searching for, either of these castings will certainly deliver. With our Race Ready ñAs Castî 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 ñMagnumî 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 rpmÍs (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 AFRÍs trademark .750î thick cylinder head deck, reinforced rocker stud bosses, and are equipped with premium one piece stainless steel 2.300î intake valves and 1.880î exhaust valves. Standard combustion chamber volume is 119ccÍs on the 345 ñAs Castî 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 2Á rolled valve angles and 1î longer head bolts needed on four bottom exhaust bolt holes. Chevrolet Big Block - 357cc Competition Package Ported Heads, Assembled - 121cc Combustion Chambers