Not sure if it has ever been done. But I know on cars like an EVO, they have a turbulator strip on the top of the back window that helps supply air to the wing by making little vortexes of air.

I also know that when you are mixing gas and air you want the best possible atomized mixture for a good combustion.

So what about adding little fins, around the circumference of the valve face inside the head, where it wont cause clearance issues.

I would think that little vanes on the valve where the fuel/air pass over would be atomized more with little to no restriction.