[Schurkey]

It's "lash" for hydraulic and solid lifters UNTIL you pass the "zero-lash" point with Hydraulics. Then it's "lifter preload". (When you pass the "zero lash" point with solid lifters, it's called "engine doesn't run right, valves don't close properly".)

With hydraulic lifters, getting to the zero lash point is the tricky part. Any monkey can add a measured amount of preload AFTER the hard part (finding zero lash) is accomplished.

One of several advantages to using aftermarket "polylocks" is that it makes finding the zero lash point heaps easier. With little friction between the nut and the stud threads, a person can just spin the nut down with their fingers and "feel" for the increased resistance when the lifter plunger starts to collapse. (Of course, the lifter being adjusted would have to be on the base-circle of the cam.)

You'd better have some experience with setting lifter preload before you try to use Cliff Ruggle's suggestion of going "up" from the point where the lifter plunger is bottomed, instead of the usual procedure where you go "down" from zero lash.