The horsepower of a 1987 Oldsmobile 455 Rocket varied depending on the specific model and whether it was a naturally aspirated engine or had some modifications. There wasn't a single 455 offered in 1987 Oldsmobiles. The 455 was phased out of production years earlier. By 1987, Oldsmobile used smaller displacement engines like the 307 cubic inch V8.
Therefore, there's no definitive horsepower figure for a "1987 Oldsmobile 455 Rocket" as that engine wasn't produced that year.
