Kazbaeden said:

A ft-lb is simply a measure of the amount rotational energy exerted to lift a one pound object one foot into the air against the acceleration due to the force of gravity.

This Rotational Energy can also be expressed in Joules (Newton-Meter).

Ugh. Sorry, wrong answer

Unfortunately, the unit lb-ft (usually called ft-lb in my experience) is used for two completely different concepts. The one you described is a measure of energy. The one that's used in most car spec sheets is torque. Completely different thing.

First, a little background. Force is a measure of how hard something is pushing linearly. A 10 lb weight pushes down with a force of 10 lbs.

Torque is the rotational version of force. It measures how much effort a rotating shaft can exert.

Imagine you've got a shaft with a nut welded onto the end of it and you put a wrench on it and pull. If the wrench is a foot long and you pull on the wrench with 10 lbs of force, you're exerting 10 ft-lbs of torque.

Anybody who's ever tried to move a stuck nut knows you get more "leverage" (by which we really mean "torque") with a longer wrench. So, what happens if you apply the same 10 lbs of force to the end of a two foot long wrench? You get 20 ft-lbs of torque. You could also get 20 ft-lbs of torque by applying 20 lbs of force to the end of a 1 foot wrench. Or 40 lbs to a 6 inch wrench. Or 5 lbs to a 4 foot wrench. Just take the size of the size of the wrench (sometimes called the "lever arm") and multiply by the amount of force you're applying to the end, and you get the torque you're applying to the shaft.

Now, imagine the shaft's got nuts on both ends, and two guys each have a wrench on their respective end. One guy has a 2 foot long wrench and he's pulling with 10 lbs. The guy on the other end has a 6 inch wrench and he's trying to keep the shaft from turning. He'll have to apply 40 lbs of force to the end of his wrench to counter the 10 lbs of force the first guy is applying, because both of those combinations multiply out to 20 ft-lbs.

Anyway, this is basicly what's going on in a car. The piston is applying a force to the crankshaft, with maybe a 2-inch lever arm. This generates torque. This torque is transmitted through the transmission, differential, etc, until it gets to the tires, which apply a force to the road through, for example, an 8-inch lever arm (for a 16 inch tire).

Guess what happens if you apply 100 lbs of force to the end of a 5 foot wrench? You strip the nut, that's what happens, ha ha!