Why were the horsepower ratings on engines often under-rated?
There’s 2 reasons for this: Reason 1: Insurance purposes. Insurance bean counters look at tables and statistics to determine insurance rates for various cars. One of the factors in determining how to rate a car is “Factory advertised horsepower”. The factory said the car makes 290 horsepower. In reality it makes closer to 350. Oops. Reason 2: Classification for Racing. In some forms of racing (Drag racing) cars are classified according to “Factory horsepower”. Again, if the car is rated at 290 horsepower (but really has 370 horsepower) and it’s going against a car that REALLY DOES have 290 horsepower. Oops.
