400 cubic inches to start with helps allot and they are long stroke, have long rods, and heads that have good low lift flow but not great flow in the higher lifts. Therefore they have good low end torque but don't rev real high cause they can't breath good up high. The 400 Pontiacs aren't really much better than the average 408 mopar. The Buick has 455 cubic inches on it's side so naturally it's a torque monster.