Depending on your P&P job to compliment your larger valves... Just putting in a larger valves we see about 3-5 cfm difference on the flow bench, cutting at the angles mentioned above was 10-15 cfm difference, P&P, larger valves, and cut properly was 20-25 cfm difference..
Stock cfm was about 45-50 cfm... After all work was done 65-75 cfm... with a 27/25 valve combo...
The biggest difference was at low lift from .050-.200 it got up there a lot quicker in cfm.
Depending on the head you are using... The 14cc head needs a lot of work to flow good, the 18cc head needs work not as much as the 14cc and the 22cc head needs a good P&P and larger valves to be the flowing at its best...