The internal combustion (IC) engine has been the dominant prime mover in our society since its invention. An internal combustion engines such as gasoline or diesel engines are a power source for many applications like automobiles, ships, aircraft etc. IC engine will be the backbone for vehicle powertrains even in the foreseeable future. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion of fuels applies direct force to some component of the engine. The force is applied typically to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance, transforming chemical energy into useful work. Simply, its purpose is to generate mechanical power from the chemical energy contained in the fuel and released through combustion of the fuel inside the engine. Design of I C engines component is not similar to as other mechanical components. I C engine system consist of many parts we will try to cover the design of certain components in this course where basic principles can be applied. Mainly includes cylinder, piston, connecting rod and crank shaft. An extensive application of I C engines worldwide shows its importance to learn this course by an engineer