Model 15 Big Valve HeadsTHE BEST BIG VALVE MODEL 15 HEAD YOU CAN BUY (here's why) So Many Think Putting Big Valves In a Head and Doing Some Grinding Makes a Good Head. There is So Much More to It. These heads are Completely CNC Ported with 1. 250" Intake Valve and 1. 125" Exhaust valve and dual valve springs. (Note if you order with Roller Rockers there will be an additional $15. 00 charge for better valve springs) Epoxy Filled Intake Bowl To Optimize Velocity The Only Head