To facilitate controlled, reproducible testing for nitric-oxide (NO) generation, a mechanical analog for the spark-ignition was designed, instrumented and tested. The analog provides for constant-volume combustion followed by product-gas expansion through a cam-driven poppet valve, giving pressure-time histories like those of spark-ignition engines. Measurements of NO concentrations in the product gas were made several seconds after combustion both with and without product-gas expansion. Ultraviolet absorption was used to monitor these NO concentrations. Efforts to measure NO concentrations during constant-volume combustion were impeded. by unanticipated strong background absorption by CO2. (Modified author abstract)