The RGR/JPC Stage 1 CNC Stage 1 heads (from $1,995.95) feature CNC-machined ports for better airflow over stock, a competition valve job, machined stock intake and exhaust valves; new springs, locks, retainers, and valve seals. The idea behind these heads is improve airflow and air velocity through the intake and exhaust ports. With the camshafts increased duration, this point is further driven home. Camshaft duration is the length of time the camshaft holds open the valve. Thinking of an engine as an air pump, with increased airflow and air velocity, and more air thanks to increased duration, more power will definitely be a result.