The effect of various intake ports are investigated in a spark-ignition engine. The flow characteristics of four-valve cylinder head were first examed in a steady flow rig for different intake ports. Tumble strength of intake configurations with different entry angles were quantified with a tumble meter. The tumble flow and turbulence in the four-valve pentroof combustion chamber are measured under motored conditions with laser Doppler velocimetry. The combustion characteristics were examined in an operating multi-cylinder engine. Lean operating limit of real engine is identified with the information on the cycle-by-cycle variation.