IMO, it has little to do with it on it's own. VE is the actual empirical result of everything. Machine work quality, assembly, ring seal, chamber/piston interaction, valve job, ignition, port (meaning from the back of the intake valve to the carb or throttle body butterfly), exh system, carb design and calibration... The cam does affect all that but what it does is more about what rpm the VE peaks, and how long the peak is maintained rather than adding a ton to it. As all the parts and labor get better, the fast rate cams lose ground against just larger lobes that dont let the valve bounce. The fast rate stuff becomes almost moot when the lift is larger and the rpm potential is raised because regardless of what the lifter diameter is, you have to lift a valve fast to get it .700" and hold it open for 280° at .050.