Most of the engines are free running engine (Valves are not damaged if timing belt breaks).Eg mehran, khyber, cultus, indus corolla, balneo etc. In interference engines , the valves are damaged if timing belt breaks. Eg santro, hiace, hilux. Timing belt/bearing must be replaced with genuine one in time. Normally, it should be replaced at 1 Lac KMs or whatever mentioned in the book. However, new hiace, hilux belt is replaced at 1,50,000 KMs as its book says.