8. Ford Mustang Boss 429
The mythical Mustang Boss 429 is a proper muscle car legend. Ford conceived the car in 1969 as a pure racing engine intended for use in NASCAR championships. The Boss 429 featured a totally different engine architecture than the rest of the Ford big blocks. First, the Boss 429 was much wider and had semi-Hemi combustion chambers.
And that helped it achieve higher revs and better flow inside the head. So ultimately, it produced more power and torque. Rated at 375 HP by the factory, this unit produced over 500 HP in reality and much more in race trim.
Ford decided to put this engine into the Mustang, creating a limited production Boss 429. However, NASCAR decided not to homologate it since the series only accepted intermediate and full-size cars, and the Mustang was a pony car model.