A model has been developed for simulating the combustion in a three-valve stratified charge spark ignition engine. The conservation equations for mass, momentum, chemical species, and energy are numerically integrated for a one-dimensional flame using an empirical model for turbulent diffusivity. The chemical reaction of the fuel and air is modeled using simple kinetics in a one-step reaction and experimentally determined ignition delays are used. Nitric oxide emissions are calculated using a simple Zeldovich model with steady state atomic nitrogen and equilibrium atomic oxygen. Effects of various assumptions and parameters in the model are discussed and comparisons with experimental data from a single-cylinder engine are presented.