On the left is the gear-drive cam and its distributor drive gear, while the pair on the right are for conventional chain drive. Notice the different helix angle of the gears. See All 3 Photos ...

We take a look at Milodon's simple geardrive system , which links the cam and crank together for better valvetrain performance from your Chevy engine - Super Chevy Magazine ...

From the December 1969 issue of HOT ROD: These cam gear drives helped move the industry forward.