Hydraulic lifters are designed to run some pre-load. If you're not sure if you have any or not, you should probably take the time to do a proper adjustment to be sure. It's not a difficult task, and doesn't take long.
One trick though. Over the years, it has been generally accepted that you tighten the adjuster nut down until you can't spin the push rods with your fingers. But with modern materials and lubes, you can often spin the rods after they're adjusted properly, so that doesn't work any more.
To find very lash, tighten the nut down with your fingers until you can't turn it any more. That's zero lash.
Here's some complete instructions:
http://www.compcams.com/Technical/In.../Files/250.pdf