There’s a reason why I’m not even mad at this dude building the visually worst-running BMW I’ve ever laid eyes on. It actually has to be one of the most ambitious engine builds I’ve heard of. This dude put rotary valves in his ‘90s 328is.

No, not a rotary engine. That would be child’s play compared to rotary valves. It’s a term that doesn’t even make sense to most casual car enthusiasts, as it just never comes up. All normal cars have valves that go up and down. They could have pushrods that actuate them. They could have an overhead cam that actuates them. They could have hydraulic actuators that, uh, actuate them. No matter how high the tech, the principle for a valve is the same in just about every internal combustion design.

But there are a few oddballs out there. I don’t have time to praise the smooth quietude of sleeve valves and other weirdos, but I can say that rotary valves are one of the stranger ways to get air into an engine and exhaust out of it.

Rotary valves aren’t all that complicated in theory: they themselves are cylinders with passageways in them. The cylindrical valve rotates, and as it rotates in time, these passageways open up to function in the way that a normal engine’s intake and exhaust valves would. Reading the wikipedia for them might be better than my explanation, but hey, I dunno.

Why do car companies not choose rotary valves? Well, watch this guy’s BMW test run and decide for yourself.



He said he was spinning tires in second, at least until the oil on his exhaust caught fire.

Why is there oil everywhere? Our intrepid rotary-valver explains in another YouTube description:
"All the smoke is from the oil going to the valves as a precautionary measure to prevent any seizures."