* Year of manufacture: Engine technology and tuning changed over the years.
* Specific application: Was it in a car, boat, or truck? Different applications often had different horsepower ratings.
* Modifications: Has the engine been modified (camshaft, heads, intake, exhaust)? Modifications drastically alter horsepower.
A stock, fuel-injected 454 from a specific vehicle might have a factory-rated horsepower somewhere in the 250-450 hp range. However, heavily modified versions could easily produce well over 500 hp, or even more with extensive modifications. You need to specify the *exact* engine and application to get a precise horsepower figure.
