340 stroker 422

Too many variables because DCR uses the intake closing event. So what influences how much air [ by weight ] is drawn into the cyl until the int valve closes:
- cam overlap [ LSA ]
- lobe lift
- how well the port flows
- the exh system
- the intake manifold flow characteristics.
All of these parameters will affect the total amount of air the cyl captures, but DCR only uses the IVC point.
The OP has 'nicely ported' RPM heads. This alone you would expect would flow better than stock heads, yet the DCR number would be the same!