Yes zero lash is no play and you can hear it. 1/4 to 1/8 turn at a time, or less when you get close and wait a few seconds until the lifter settles to be sure. I've always done hydraulic lifters while running and hot. Low idle though or you are going to need a bath in solvent.
If your engine is cold and you adjust, you may get an over tight condition when it gets hot.
I'm a V8 guy, maybe a 6 guy can confirm.
