The development of combustion system using a cast head normally takes quite a long time and quite an amount of money even if a single cylinder facility is used. The application of rapid prototyping technology to the combustion system development can reduce the time and cost of the development due to the elimination of a wooden pattern and casting process.The aim of combustion system development (specially port development) is to impart proper turbulence intensity around the spark plug at the right time. There are large body of data correlating the results of steady state flow rig test with engine performance. From port and combustion chamber CAD data, a resin model was made using stereo lithography apparatus(SLA). Flow rate and swirl strength were measured with the steady flow test rig, and the resin model was modified using file and clay until the satisfactory flow and swirl characteristics for the specific engine performance are obtained.The final shape of port and chamber was then fed to NC machine to produce two-piece aluminum single cylinder head with water cote between two pieces. Combustion characteristic of the machined head was assessed on a single cylinder test engine. From the engine test, the satisfactory combustion characteristics were confirmed as expected by steady flow test results.The new development procedure is proved to reduce development time by at least 4 weeks and development cost by at least $15,000. The new procedure is also proved to produce unambiguous master model since the final port shape is in CAD form.