Algodoo

It does look good, but it's still somewhat slow for an engine that runs at 360 Hz. Even if it has valves and such, i'd say you could make it much better, maybe 60 rad/S without the counterweight (make it weight a very low number), use boxes instead of those polygons and making the boxes transparent, and giving less way to the cams, then maybe making the levers that push the valves amplify the movement from the timing rods
Maybe you'll need to use Cgears, Kilinich has a generator for them somewhere

I already have many engines of your "efficient,simple" type, even this engine can run at 60 rad/s, if you fix the retarded timing at idle position(!). You could also soften the springs,fix the engine mount, lower the density of the valve parts and rods and do some other modifications. But my goal was a softly running engine, because otherwise, I wouldn't even use this variable timing thing. In this configuration, valves are timed perfectly even at max rpm if you slow down to 0.1, and the engine vibrations are relativly tiny.
It's a show engine

I looked inside an engine before and learned all about one and this one well it has almost everything from the engine I demolished... kinda