A spark ignition engine is simulated for its flow field and combustion using a modified version of KIVA-II. The code handles an arbitrary 3-D computational domain and boundary conditions in the Cartesian coordinate. The valve is fixed at a half open position and the pressure boundary condition is specified at the port upstream. The grid is generated by a 2-D CAD package and later combined to a 3-D. Post-processing is performed by a finite element postprocessor package. Results for a typical spark ignition engine show reasonable trends for the velocity field and flame propagation throughout the intake, compression, combustion and expansion stroke.