If the noise is basic lifter/rocker tapping and not extreme then yes let it run for a little while. I would bring it up off idle also, say 2000/2500 rpms a few times also during the run and see if there's a change in sound as it runs. Just don't rev it way up. 10 min. of that should surely quiet it down if it's just a pump-up problem. But as i said earlier, if the cover is off i would check for that pushrod to be loose at TDC on that cyl first. If the cover is back on then go ahead and run it.