340 cam in a 318

Farrrk.. Sometimes I don't know why I even bother to post here.
The drop at TDC is a reference point. From that reference, knowing the cam lift points at EVERY degree of crank rotation tells me how far the valve will be off it's seat ( obviously multiplied by rocker ratio) at it's closest position to the piston, which as you pointed out is not usually TDC .
Can I change the lift? Can I change the duration? Can I change how aggressive the lobe is? Can I change the LSA, what if I change the installed centerline or the rocker ratio when I'm looking to upgrade a cam without changing the base engine configuration?
Knowing the valve lift at every position of crank rotation ( piston location in bore) makes this possible.
Is this making your head hurt?
Spring pressure, valve train flex etc, usually increase piston to valve, compared to no load on the valve train..