[mr0077]

Saint71, weight and horsepower relate to acceleration, but drag and horsepower relate to top speed (unless your power/weight ratio is so low you don't have room to accelerate to top end). John Cobb's Railton Mobile Special weighed over 4000 lbs when it set the world land speed record (in the 1950's?) at over 400 mph.
RPM and horsepower are related to torque by the formula, horsepower = torque x RPM / 5252. So, if you have 400 lb/ft of torque at 5000 RPM, you're making 381 horsepower at that RPM...but if you can move the same 400 lb/ft of torque up the RPM band to 8000 RPM, you're now making 609 horses (at 8000 RPM), with the same size motor. The naturally aspirated Formula 1 engines are a good example of this...not much torque, but running at maybe 11,000 RPM(?), they make big horsepower numbers with small cubic inch displacements. Problem is, it gets VERY expensive to increase RPM, not nearly so expensive to increase cubic inches...or to increase effective size of the motor with forced induction.