* 2-valve 5.4L: Generally around 260 horsepower.
* 3-valve 5.4L: This engine wasn't introduced until later model years (around 2004). A 2001 F-150 would *not* have a 3-valve 5.4L.
Therefore, for a 2001 Ford F-150, you can safely assume the horsepower of the 5.4L engine to be approximately 260 hp. To be absolutely certain, check the sticker on the driver's side doorjamb or the owner's manual.