The 454 appeared in the Chevelle in 1970. And for one glorious year, it was the zenith of muscle car development. The "little" 454 was rated at 360 horsepower; and the king of them all, was rated at 450 horsepower. And then they were gone. The names and the displacements were around for a few years, but compression was lowered, and ratings were down. I had a 360 horse model, and I could run with anything, including the 427 'Vettes. I can only imagine the 450 horse model.