Back to our regularly schedules discussion in which the OP started.
The reason a big block wins over any small block, like I stated before is bore size. In a Normally Aspirated engine the bigger bore wins because you can run bigger valves.
There is no boost to force air in and out of an NA engine, so to make more power you put larger intake valves in them.
A NHRA 500" Pro Stock engine uses north of a 4.700" bore and a 2.500" intake valve. A NHRA Pro Stock motorcycle has a 5.25" bore and runs a 2.700" intake valve.
Big bore, big intake valve is the key to NA horsepower. Now obviously you need a port to compliment the valve size, but you get the point.
Tom
