I look at cubic inch as when the valves are closed and you're on the compression stroke. Different cams give you different useable cubic inch displacement. My 410 probably has about 313 useable cubic inches.
Jim, you're scaring me here
You are way, way off on this line of thinking. Have you ever heard of volumetric efficiency? This is the amount of air the engine uses at a given engine speed, divided by cubic inch displacement. A performance street engine can easily exceed 90% VE; 100% is not unusual. A really good race engine can see VE numbers over 125%. And yet this is with intake valves that close very late, which would result in fewer "usable cubic inches", by your methodology.
Let's say that your 410 had 100% VE; that means it would be using 410 cubic inches of air every two revolutions of the crank. In your case it might be more like 90%, so it is using 370 cubic inches of air, but it is still going to be far more than 313 cubic inches, as you suggested. Exhaust scavenging as the intake valve is opening and the ramming effect of the inertia of the air/fuel column in the intake manifold as the intake valve is closing will allow a lot more air into the cylinder at the peak torque point than just 313 cubic inches.
