Un-stroked vs Stroked Displacement vs. Crank Angle, etc.

and where you want the cam open
but gas velocity keeps going up even as piston speed starts going down (after the point where the rod is tangent to the crank throw- which is before 90 degrees ATDC more like 70 short rods earlier, long rods later (gives you more time to get the valve open so you do not have to start as far BTDC- which gives more overlap)
Thanks NM