It's the primary plates that can be drilled, not the Secondarys. The 8 degree cam timing retard that was first used in `72 on the 460 was accomplished with a reposistioning of the Keyway Slot of the Crank Sprocket, not the Cam itself. So as long as you use the correct Cam Sprocket you'll be OK. The 68-71 Sprocket can be use on 72, and up engines to advance the cam the 8 degrees back. This will boost the torque of the later 460 engines.
Posted on Jul 30, 1999, 6:45 PM from IP address 38.162.110.2