Once a new engine is designed, it is subjected to extensive development programs prior to manufacture in production volumes. Many in-vehicle and engine dynamometer tests are required to integrate a reliable powerplant into a commercial vehicle. Development engines are limited in number and built of premium cost experimental parts. To prevent the failure of development engines, adequate strength of all structural components is necessary early in the development program. This paper examines how experimental stress analysis was used in assuring adequate strength of the new Chrysler 245 cu in. 6 cyl engine.