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Same Engine, Different HP Ratings
During the muscle car heyday, many manufacturers hid the real HP rating for insurance purposes or falsely advertised power of their cars. Back in the late ’60s, GM had a rule that forbade the manufacturers to produce cars with more than one HP for every 10 pounds of a car’s weight. This rule was aimed at stopping manufacturers from producing insanely overpowered models. All GM products and brands had to follow this. The only exception was the Corvette.
In 1968, Pontiac introduced the new Firebird with a 400 V8 engine producing 320 HP. Immediately after the introduction, car fans were publicly asking the factory why this new 400 V8 engine in the Firebird was rated at 320 HP, while the same 400 V8 engine in the GTO was 366 HP. Pontiac didn’t reply and soon the answer came from the insiders from the factory. The new Firebird 400 weighed 3,300 pounds.
So, to make it eligible under the GM one HP per 10 pounds rule, Pontiac had to rate the 400 V8 engine at 320 HP. Pontiac knew car fans would see through this stunt and the dealers would explain how the new Firebird 400 was significantly more powerful than stated. However, they needed to do it in order to sell the new model to the general public.