Valve to piston clearance

No, the hydraulic lifter plunger will bleed down when you put a load on it....

Some people tear them apart and make a solid shim to hold the plunger in place to keep it from bleeding down and making your measurements incorrect...

If you could set the plunger at it's bottom and then set your adjustable rocker to zero lash it could work...

The goal is to keep the plunger from moving down when you are measuring... It can throw off your measurements..
I dont have adjustable rockers i have factory ones. But I have a bunch of used lifters I can take the guts out of. I also plan on making some light valve springs to do the cam decreeing