If anything, a gear drive would waste more energy than a chain and sprocket. The chain and sprocket is one of the most (if not the most) efficient ways to transmit power.Do Nascar motors use them? 6 cylinders use them but they don't rev like a V-8. Grumpy Jenkins used a nylon gear timing chain setup in his old Pro Stock motors. Not sure about the harmonics part but everything I have read says no power gain. I think it just comes down to wanting the sound (or not).
I imagine the slop, however minimal it is, comes from distance variations between the rollers. BTW, I'm not referring to stretch here.I'm not sold on the precision timing thing. The valve springs put so much load on the camshaft that it has to be dragged around by the crankshaft so where does the slop come from? I can't see the cam ever trying to spin faster than the crank.