Valve Drop and Piston to Valve Clearance

I’m not sure why anyone would go through the process of building any engine and stab a cam in it on a guess. There are so many factors involved that can effect P to V clearance that any amount of math and “figuring” is a guess at best. Measuring is the ONLY way to KNOW how much room you have. And when someone asks me “what’s the biggest cam I can stick in _____ (Enter whatever engine you’d like)? I just shake my head. Now there is some relevance in knowing an appropriate clearance distance before picking a camshaft, but hopefully you picked a piston that makes that a little easier. As a general guideline if you have stock pistons you have no business installing a cam that’s even close to hitting. It’s a package.