Culminating several years of disciplined effort, this paper describes the engineering program preceding the introduction of the Transamerica Delaval R5 diesel engine to the marketplace. This engine enters the large-bore medium-speed class rated at 634 kW/cylinder (19.0 bar bmep at 514 rpm). Careful design, followed by an aggressive test strategy has produced an engine of sound integrity. Mechanical endurance testing was followed by a thorough inspection of all major components, revealing excellent wear rates. This paper includes basic engine design, residual fuel testing, emissions and performance information.