Airflow to Cubic Inches

Is that formula ideal ? Don't know but it seems reasonable.

Definitely there's no ideal air flow just to cubic inches, you have to factor in rpm and volumetric efficiency for what I call dynamic displacement the size of the engine at any given rpm (cfm).

Basically cid x rpm / 3456 x ve% = cfm is what you engine roughly dynamically displaces but there's no easy way to figure needed head flow from that.

Are you trying to figure out head flow for any particular build ?