An internal combustion engine includes a cylinder head and rocker box assembly that includes a duct arrangement that removes blow-by gases. In a first embodiment, a duct is formed from the upper surface of the cylinder head aligned with an opening in the bottom of the rocker box and proceeds to horizontal sections leading to a fitting with a line leading to an intake manifold. In a second embodiment, a single straight duct includes a straight angled portion extending downward at an oblique angle to the upper surface of the cylinder head to an intake port in the cylinder head. Action of the engine draws the unwanted gases from the rocker box through the opening of the ducts to an intake of the engine.