The Webster and kerzel open crank hit and miss engines can be found on the web if you want something small.
Model Engine Builder will sell the two back issues that have very good drawings for the Zero-six engine in digital format for a modest cost. I built it with some modifications so it did not look so much like a barstock engine but mechanically all the same.

Jerry Howell's "farmboy" is also a nice looking opencrank from barstock and ideal for those that like making aluminium swarf
Edited By JasonB on 26/03/2019 12:36:46