20. Pontiac Firebird 400
When Pontiac first unveiled the Firebird, it caused quite a stir among performance-loving car buyers in America. It was a coupe with a wide arrange of optional extras. Also, it came with one of the biggest engines you could get in a pony car, the Pontiac 400 CID V8. But back in the late ‘60s, GM had a reasonless rule that forbids manufacturers from producing cars with more than one unit of horsepower for every 10 pounds of the car’s weight.
The aim of this rule was to stop manufacturers from producing insanely overpowered models, and all GM products had to follow it. The only exception was the Corvette. In 1968, Pontiac introduced the new Firebird with a 400 V8 engine they rated at 320 HP. Immediately after the introduction, car fans were publicly asking the factory why the new 400 V8 engine in the Firebird was rated at 320 HP, while the same 400 V8 engine in the GTO made 366 HP.
Pontiac didn’t reply, but soon the answer came from the insiders from the factory. The new Firebird 400 weighed 3,300 pounds. So, in order to make it eligible under the GM one HP per 10 pounds rule, Pontiac had to rate the 400 V8 engine at 320 HP.