variable cam timing old school

[Lynn]

In today's electronically controlled engines, variable cam timing is common.

I remember seeing an "Honest Charley" ad late 60's or early 70's for a lower timing sprocket for SBC engines that retarded the cam timing with rpm. I have never seen one, but my understanding was that it worked by centrifical force pushing spring loaded weights out farther and farther with speed. It wasn't just multiple fixed keyways. Don't know if it fit under the stock timing cover.

Anyone ever see one? Are they still around? Down side?

Seems like a good idea.