Blowers, wheezers, huffers—whatever you choose to call them, these terms refer to Roots-type superchargers. In the 1800s, the Roots Company in England originally invented the supercharger to pump fresh air into and stale air out of mineshafts. General Motors took notice of this technology in the ’40s and realized that the Roots design could force more air into its own diesel engines, giving GM trucks more power than their competitors. Hot rodders realized back in the late ’50s that they could do the same for their racing engines. Blowers are now commonly used to provide a 25 to 50 percent increase in horsepower to typical small-block Chevrolets. Roots-type blown engines provide a push in the back unlike anything short of another type of supercharged engine, and nothing else sounds like a blown engine at full throttle.
Of course, we realize there are other superchargers on the market today, including screw and centrifugal styles, but to keep our explanations simple, we’re concentrating on the Roots-style blowers here. Watch for articles that feature other styles of superchargers in the near future. But for our example here, know that regardless of the treatment or efficiency comparisons of forcing more air into the combustion chamber, a supercharger in its basic form is an additional air pump sitting atop the motor.
Most Roots-type blowers have a positive displacement, meaning that their output increases at the same rate as engine speed. Roots-type blowers produce boost in a linear manner that increases proportionate to engine speed. In other words, they have to build up to their maximum boost, but because the blower is always being driven, it is constantly building boost, even at low speeds. Therefore, throttle response is instant, which makes blowers very popular with hot rodders.
The only drawbacks to blowers are that they use horsepower from the crankshaft, and a typical supercharger setup on a small-block Chevy can weigh up 100 lbs or more. However, even though it takes as much as 75 hp to run a modern Roots-type supercharger, it makes enough additional horsepower that the losses aren’t really felt. The additional weight penalty can be trimmed away in other places as well. Many hot rodders feel that no matter what the losses or weight penalties, a blower sticking up through the hood with its square-cut gears whining for all the world to hear is pure heaven and nothing else will do.