The objective of this project is to develop a low emissions natural gas engine. The emission targets for this project are 0.27 g/kW-hr (0.2 g/bhp-hr) of NOx and 0.013 g/kW-hr (0.01 g/bhp-hr) of particulate matter. To meet the objective, a chemically correct combustion (stoichiometric) natural gas engine with exhaust gas recirculation (EGR) and a three-way catalyst (TWC) was developed. In addition, a Sturman camless Hydraulic Valve Actuation (HVA) system was used to improve efficiency. A Volvo 11 liter diesel engine was converted to operate as a stoichiometric natural gas engine. Pistons with a 14.3:1 compression ratio were used on this engine. Illustrations. This is a print on demand edition of a hard to find publication.