The engine shown at the link you provided uses a crankshaft rotary valve. There are many air/steam engine designs that use a similar type of valve.
Try having a look at the Elmer's Engine forums on Yahoo Groups. There are 4 forums and the plans are in the Files section. You'll probably have to register with the forums to gain access to the files section.
Here is a youtube video of a single cylinder engine that uses the same principle as the radial engine in your video. Plans for this engine can be found on the Elmer's Engine forum I listed earlier.