Abstract: A self-contained, hydraulically operated clutch-type coupling, allowing a minimum of two vehicular type internal combustion engines to be mounted in tandem replacing the standard single block, multi cylinder engine. Flexibility is provided to the driver by a computerized control system to select operation of one or more engines to produce minimum to maximum horsepower at the flywheel, necessary to meet specific road and traffic conditions while maintaining a constant engine (RPM) speed. In one embodiment, a single engine is started to minimize undesirable emissions due to the combination of cold start conditions and wall quenching and fuel conservation purposes. Upon attaining engine operating temperature uniformity, the succeeding engine(s) can be started and operated to provide maximum available horsepower/torque to meet road load conditions.