Chrysler built the 426 Hemi to win NASCAR races and had no intention of selling it to the public. A homologation rule forced the company’s hand, and for six model years a lightly civilized race engine was available over the counter to anyone who could afford the option and the insurance. Here is what made the Elephant so effective, what the 425-horsepower rating really hid, and why 1971 was the end of it.