When I was a young lad, my father bought me an Erector's Set for my
birthday. What a fun time we had with that, building things, screwing
things together, taking them apart again and again and again. He also
bought me the plastic model known as 'the Visible V-8 engine' which
operated like a real V-8 engine. My brother and I would sit for
hours watching that engine go round and round, pistons going up
and down, crank shaft turning, what FUN!

Visible V8 Model Engine Kit