27. Iron Duke
It is strange to see this four-cylinder engine amongst the high-powered V8s on our list, but we had to feature it since it was a very important engine. The importance of the Iron Duke lies in the fact that it was one of the very few four-cylinder engines produced during the late ’70s and ’80s, and even though it wasn’t very powerful, it was successful and made in millions.

It started life in 1977, and Pontiac first used it. Displacing 2.5 liters and delivering just 84 hp, it was nothing to write home about. But in the Malaise Era, the design, output, and fuel economy were just the Pontiac needed, and the engine proved to be popular and steadily improved over the years. It stayed in production until 1993, and during that time, it powered various models from Pontiac, Chevrolet, and Oldsmobile.