Behold engineer Aliaksei Zholner‘s working V8 engine, made entirely with paper (and he notes, “some scotch tape on valves to eliminate friction”). At 32 x 24 x 27 mm, it is tiny, as is this paper throttle:
Zholner has built tiny engines before. Take a look at his 80 x 60 x 40 cm V6 engine working paper model from 2014. As seen above, the balloons provide compressed air to make them run.