The $29.99 all-metal desktop Stirling engine kit is one of the simplest. It can be assembled in 15 minutes and is recommended for ages 14 and up. Also for $29.99 is the Exploring Kid Steam Engine Kit.

It’s also less complex, with 230 components, fewer than that of the V8. “The Playz V8 Model Engine is a great kit for learning about engines,” said one shopper. “It's easy to build ...

If you love the sounds and smells of an internal combustion engine but don't want to get a car to experience one, you could buy a mini engine kit and build a scaled-down example as the main feature of ...