The intake system of an internal combustion engine plays a key role to determine its performance. Gas dynamics varies with many factors, such as whether it is fuel injected or carbureted engine, temperature, runner length and diameter, valve timing, number of cylinders and others factors. A careful design of the intake system provides the engineer a possibility to manipulate the dynamics of the gas, allowing taking advantage of the engine's operation at some moments. The aim of the current paper is investigates the effects of intake runner length and diameter on the performance of a four stroke and single cylinder engine, design a three stages intake manifold for this engine and elaborate a design algorithm to find the best intake runner length and diameter configuration. The characteristics that were taken in consideration to evaluate the engine performance were the brake power, volumetric efficiency and trapped gas. The performance evaluation was made with the assistance of a 1D-simulation software called GT-Power and an optimization software, modeFrontier, where it was used to improve the efficiency to choose the best configuration of the intake runner length and diameter of each engine speed. The study showed that in some moments it is possible to achieve a high volumetric efficiency thanks to the tuning effect, which demonstrate that if adjusting the intake runner length and diameter, making the pressure waves arrives exactly at the time when the inlet valve opens, it allows to reach an extra boosting on the admission time.