A hot rod is a specific type of automobile that has been modified to produce more power for racing straight ahead. The hot rod originated in the early twentieth century in the United States and continued in popularity over several decades until a decline in the 1970s. It was then that street rods took over; the difference between a hot rod and a street rod is the intended purpose of the vehicle. Hot rods were built for racing, while street rods are built mostly for show and driving around town. Common modifications of early hot rods included engine replacements, body streamlining, and other body modifications.
Specific automobile models were often chosen to be made into hot rod vehicles because they were generally light, which meant they could be built for better speed. Roofs, especially convertible roofs, were often dismantled, and the body of the automobile was modified to be more streamlined and aerodynamic. Early hot rod models often featured engines that were taken from more powerful vehicles and placed in the lighter automobile. This provided necessary horsepower to propel the lighter vehicle forward. Steering was not a primary concern, as hot rod models were designed to go fast in a forward direction only.
Races were often held in desolate areas, especially in southern California. Hot rodding became especially popular after World War II, as soldiers returned home with specialized mechanical knowledge taught to them by the military. As cars became more powerful throughout the decades, however, manufactured cars off the assembly line were both roomier and more powerful than hot rods. The popularity of the custom cars declined because of the surge in new car technology until the 1970s when a fuel shortage occurred. People of the U.S. then began pressuring carmakers to focus on fuel efficiency, which meant the hot rod had an opportunity for rebirth.
That rebirth came, but in a different form. No longer were hot rods built for racing; instead, they were built for show, and for everyday driving. This new entity became known as the street rod, since such cars were designed for street riding rather than racing. Street rods look identical to hot rods and many of them feature the same engine specifications, though they will rarely, if ever, see a race course. Street rods are popular at car shows throughout the world, and they are built to be eye-catching pieces rather than performance machines.