Valve diameter times .25 gives you the L/D ratio at THAT particular ratio.
There are other ratios I use to determine lift. For SFT I use .31 L/D ratio. I can’t always get that much lift due to valve train limitations and what you can actually get on the lobe.
For example, I have a 2.055 valve so multiply that by .31 and that’s .637. The closest I could get was .620 lift and have a reasonable lobe.