* First Generation (1964-1967): These cars used a variety of engines, but the most powerful were the 389 cubic inch V8s. Output ranged from around 325 horsepower to over 360 horsepower in the high-performance versions.
* Second Generation (1968-1972): The second generation saw a shift to larger engines, mostly the 400 cubic inch V8. Horsepower ratings varied, but typically fell in the 330-360 horsepower range, although some Judge models offered even more.
* Third Generation (2004-2006): This revival of the GTO used a 5.7 liter LS1 V8 engine. The horsepower was consistently rated at 350-400 horsepower depending on the year and configuration, although some aftermarket modifications could increase it significantly.
In short, to accurately answer how powerful a Pontiac GTO was, you need to specify the model year. The horsepower ranged from roughly 325 hp in early models to over 400 hp in modified or later versions.
