Abstract: An improved torsional vibration isolator assembly for an engine is provided which includes a non-linear spring device which effectively minimizes the transmission of torsional vibrations to the engine's gear train throughout all engine operating frequencies and conditions while limiting relative movement between the engine's crankshaft and crank gear so as to maintain timing error within acceptable limits. The improved torsional vibration isolator is designed to absorb torsional vibrations transmitted from the crankshaft so as to substantially isolate the entire engine gear train, including the crank gear, from the torsional vibrations throughout all engine operating conditions and frequencies, including at and below the natural frequency, i.e. crank resonance, of the crankshaft. The crank gear isolator includes resilient elements positioned in cavities formed between engaging projections formed on inner and outer rings of the assembly.