**there are way too many variables involved to be able to state that 180 psi = **10:1, or anything of that sort. Cranking speed? Cam overlap? Valve lash? Air **temp? Etc.

Cranking speed doesn't affect the final PSI figure more than a fraction of a percent; it may affect how many strokes it takes to get there.

In the bigger scheme of the world's engineering, figuring out cranking compression is actually pretty easy. Rod ratio, air density, compression ratio, cam duration (specifically Intake Valve Closing) are about all it takes.

If I may ramble.. it's part of scientific experimentation to try to quantify these things. Doing such calculations should not be regarded as being beyond the average engine builder ( or rather, parts/specification selector).

Having a consistent, (if at the root empirically derived) rule of thumb for what might be the ideal intake and exhaust port cross sectional area per displacent and RPM range... or having a certain aim in mind for cylinder pressures achived are both examples of knowledge that can be used across various brands and families of motor, to compare & contrast.
In fact, doing so can be the best method to select areas for modification.