Modern Muscle / ModernMuscleXtreme.com CNC ported heads are unmatched in performance and endurance. Relying upon over 40 years of HEMI experience as it applies to drag racing, and other competitive automotive sports, our heads are sure to exceed your expectations. Our custom porting process is done using state-of-the-art CAD/CAM software to ensure maximum flow performance and consistency across all of our parts.