The 1970 Chevelle LS6 made a factory-claimed 450 horsepower, with some reports suggesting the real number was closer to 500. By 1972, GM’s own base wagon was outselling every SS performance package in the lineup. Insurance rules, lower-octane fuel, and a new net-horsepower rating system all played a part. Read on to find out exactly how much power the Chevelle lost in just two model years, and why.