Abstract: An air intake system for an internal combustion engine, particularly for a diesel engine containing a cylinder having a combustion chamber therein, is disclosed. The system comprises a spiral-shaped intake port formed in the cylinder head. The spiral-shaped intake port introduces intake air into the combustion chamber and compulsorily produces a swirling motion of the intake air while the air passes through the intake port. The system further comprises a baffle or baffles for attenuating the swirling motion of the intake air to an optimum level prior to the intake air being sucked into the combustion chamber.