Troy wrote: "I'm not so sure your method of determining hydraulic lifters is accurate, but I really don't know. Maybe get a second opinion."
Second Opinion:
Yup. That's how you do it. If the lifters are stock, solid lifters and you run the valve adjuster in to zero clearance, it won't go anymore, period, because you've bottomed out the push rod and (solid) lifter.
If it has hydraulic lifters and you turn the adjuster to zero clearance at the valve stem, you can then keep turning a number of turns as the push rod makes the lifter piston collapse, then back it out 1/2 - 3/4 of the collapsed length (you have to count turns, here) and you're done. There is a spring inside the lifter to provide the proper "rest" pressure. The VW techs would set them at any engine temp by relieving pressure from the valve stem adjuster, then turn it back in 1 or 2 turns, no more, and they were done. Once they're adjusted you really never have to check them again, but this group probably would! It's important to know that hydraulic lifters give you zero clearance between the rocker arm adjuster and the valve stem at all times, hot or cold, but they automatically adjust for oil/engine temp changes, keep a pre-determined pressure against the valve stem when "closed" and a stronger pre-determined pressure against the stem when pushing it "open". They're usually quieter running because of this.
I'm also seventy and adjusted lots of valves on all manner of VW’s (but sadly, no aircraft motors).