The Honda K-Series engine was introduced in 2001, replacing the B-Series as the engine of choice for Honda enthusiasts. These new K-Series engines are the most powerful stock Honda/Acura engines you can get. They featured new technology including a roller rocker valvetrain, better flowing heads, and advanced variable cam timing technology that made these engines suddenly the thing to have. And that's where the engine swappers come in.
If you have an older chassis and are looking for a serious injection of power and technology, swapping a K-Series engine is a great option. Honda K-Series Engine Swaps will tell you everything you need to know.