This article is pretty much wall-to-wall snake oil. The bit at the end is just completely false. Some people, who hadn't really bothered to do the math at the

This article is pretty much wall-to-wall snake oil. The bit at the end is just completely false. Some people, who hadn't really bothered to do the math at the time, believed fifty years ago that spring-closed valves would float at high speeds and desmodromic valves were the solution. But that isn't true: metallurgy marches on, and nobody has been seriously impeded in making an engine turn at any desired speed with valve springs. Motorcycle engines turn at stupefying speeds without experiencing valve float. In practice it's actually the desmodromic designs that are troublesome, because of all that moving mass. Anyway, there are lots of other dumb claims in here, like nobody has ever done variable timing of exhaust valves, which is obviously not true.