A computational fluid dynamics study of the internal flow within a four valve pent roof spark ignition engine has been carried out. The code allows a full 720° cycle to be run and two cycles were run to eliminate the dependence upon initial conditions. The engine was run with two different ports to give a high barrel swirl ratio of 1.7 and a low barrel swirl ratio of 0.4. The results were compared with two previous experimental studies performed using laser doppler velocimetry and hot wire anemometry.The comparison for the two configurations proved that for both cases good qualitative results could be obtained and for the high swirl case good quantitative results as well. The code has proven itself in the validation exercise and can be used with confidence in further design applications.