Back in 1970, Pontiac introduced a series of changes to the engine lineup available on the Grand Prix, replacing the 428ci (7.0-liter) previously sold as optional for MY 1969 with a new 455ci (7.5-liter) V8 that developed 390 horsepower. On the other hand, the base Grand Prix continued to be offered with a 400ci (6.6-liter) developing 350 horsepower, but the all-new 455 was the preferred choice for everybody looking for a boost of power.
