I still have a Cox .049 engine in the basement somewhere.

Used to see adverts for those in magazines and even (iirc) comic books

Of course that's .049 cubic inches (~ 0.82 cc), huge compared to the one in the article.

I also had an .020 engine, but it never ran very well, and I don't know what happened to it.

I had a lot of fun designing my own airplanes and flying them with the .049. Modern electric airplanes are too easy.

Outerzone is a great site for (mostly vintage) model aircraft plans.

Cut my fingers up many times as a kid trying to start Cox model airplane engines…