Abstract: A system and method for supercharging an in-line engine is disclosed. The system comprises a "bolt-on" supercharger system that is attachable directly to an existing installed engine without significant modification of the engine. The system includes an intake manifold fabricated preferably from aluminum and appropriately sized to the particular engine and available space, and which is removably attachable to the stock intake manifold of an engine in flow communication with the stock intake manifold; a supercharger removably attachable to, and in flow communication with, the fabricated intake manifold, by use of an adapter plate; a bypass valve assembly attached between and in straight line flow communication with a carburetor or fuel injected system and the supercharger. The bypass valve is joined to the carburetor by a bypass adapter ring, and allows an air-fuel mixture from the carburetor to bypass the supercharger and go directly into the fabricated intake manifold when the system is not in a boost mode.