Chess King is optimized to use a custom version of Houdini 2 to maximize its power and speed. Chess King pro uses the most powerful engine Houdini 2 Pro. Note: if you really would like to use another engine, you could edit the file engines.xml file or simply rename the new engine. But we’re not too sure why you’d like to do that since Houdini 2 is the most powerful engine available todate.