PROCOMP BIG BLOCK CHEVY ALUMINUM 360/125CC 2.25/1.88 CNC PORTED BARE HEADSCALL SHANON AT 507 445 3235 WITH ANY QUESTIONS. PC3028 2 BARE CNC PORTED Aluminum Big Block Chevy Pro Comp Motorsport Heads Manufactured from 356 T6 aluminum Have Accessory holes to except factory accessories. 360cc Intake Runners 125cc Combustion Chamber Intake flow is 404 CFM at . 800 *Flow numbers are approximate. Exhaust flow is 307 CFM at . 800 Spring pads machined to 1. 740 to except the largest roller springs *750lbs. Max. Bronze Valve Guides