For some, learning by example is the best way to get info sealed into the noggin. If engines are the thing they want to learn about, then Matt Keveny's site, Animated Engines, should be the first stop.
Unlike the engines profiled, the site couldn't be simpler: clicking one of the 21 different engine types will take you to a page demonstrating how that engine creates power. The animations can be run anywhere from one to 25 frames per second to provide a crystalline breakdown of an engine's combustive ballet.
There's even knowledge for the engine expert, with animations detailing some forgotten freaskshows of the pistoned world, including the Unknown Beam, Low Differential Stirling and Crank Substitute. Head on over to check out some line-drawing gearhead pr0n.