A drive system for an internal combustion engine including an endless chain connecting a drive sprocket on a crankshaft to a driven sprocket on a camshaft. The drive system is comprised of at least one balance shaft and a torsion bar. The balance shaft has a first end for connection to the drive sprocket and a center bore. The torsion bar is located within the center bore of the balance shaft. The torsion bar has a first end for connection to the drive sprocket and a second end fixedly attached to the inner end of the center bore. The torsion bar absorbs torsional vibrations and isolates torsional vibrations due to inertia of the balance shaft caused by the crankshaft. Bearings are located between the first end of the torsion bar and the center bore of the balance shaft, to center the torsion bar within the balance shaft.