The 2003–2004 5.9L Cummins Cylinder Heads uses a cast-iron, 24-valve. It holds the intake and exhaust valves, springs, and rocker arms. Each valve has its own rocker arm, which improves control and makes service easier.

These heads are strong and flow well, working for both stock and modified engines. Performance builds may need porting or stronger valve parts to handle more boost and pressure. Heat can cause cracks or warping, so good cooling and maintenance are important.