I’m a bit skeptical about the stream engine just because it requires not just metal working but precision metal working where a piston needs to form a seal with the tube it’s in not just at one place but anywhere it moves in that tube, to spin a shaft without wobbling to the point that it comes apart at the intended speed. Even more difficult if it needs to be hardened, since a bit of warping is common during a quench.

I think it’s easy to take a lot of things for granted and miss that modern (or even just industrial age) things aren’t just the result of advancing a single tech tree but multiple tech trees coming together at the same time. Like I didn’t even go into the lubricants and gaskets a motor requires.