The crankshaft system of engine is a complex vibratory object and its vibration modes are consisted of torsional, axial and their coupled vibration. Among them, the torsional vibration causes engine noise as well as serious fatigue faillures of crankshaft. If the troules of noises and crankshaft strength are forecasted by torsional vibration calculation in the design atage of crankshaft, the torsional damper is adopted as the final countermeasure. In this paper, some computer program to calculate crankshaft torsional vibration of engine are developed and with developed programs, an efficient rubber-viscous damper for automobile and with developed programs, an efficient rubber-viscous damper for automobile engine is designed and manufactured, and then it is fitted on the actual automobile engine to confirm its calculated efficiency. By comparing the measured result (with damper and without damper) with the calculated one, the reliability of developed computer programs and the performances of manufactured damper are confirmed.