1966 Dart D-Dart cam spec

rumblefish360 said
The cut down the base circle even more. (There is a limit of course.) If you take a peak at large roller cams, there base circle is nearly down to the maximum, practically sitting the lifter on the uncut portion of the cam.

That is correct, that is how they ground the cam on my early dodge hemi, old school methods of making them thump.