Performance and Sound
Since all American cars were under attack from environmentalists in the 1970s, the muscle car performance from only a few years before was gone. It means that no matter how powerful the Gran Torino looked like, it needed to be faster. To make it look fast and have smoky burnouts on the set, technicians installed higher gear ratios so the car could accelerate quicker and easily roast the rear tires. In stock form, the 1974 Gran Torino could reach 60 mph in about 8.5 seconds. But it could do much better on TV with a different gear ratio (via Barett Jackson).
Another interesting detail is the sound. The rumbling of a V8 you hear when you watch this show is not the actual 1974 Gran Torino engine sound. Like the performance, the sound of the engines suffered from emissions regulations in the mid-1970s. So, the production crew recorded sounds of earlier, more powerful Gran Torinos and dubbed them over the shots of the Starsky and Hutch one.