That is an unusual noise for rocker arms, but it might be worth another look inside to make sure they are all in adjustment. The position of the valves will definately effect whether you get a loose or tight feel on the push rod, hence the procedure is based on the firing order and knowing when the valves you want to adjust are closed (on the base of the cam, not on the lobes). If you have roller rockers be sure and inspect the roller tip for wear / slop.
Edit: Here's a pretty good video on pedestal mount rocker arm adjustment
http://www.youtube.com/watch?v=z8NW0R0kDiY
Edit: Here's a pretty good video on pedestal mount rocker arm adjustment
http://www.youtube.com/watch?v=z8NW0R0kDiY
well if you are only hearing it at a certain rpm. take off the belt, start the car and get the car up to that RPM and see if the noise is still there. if you hear it. obviously its not an accessory and you can rule it out. but remember the water pump wont be rotating but you will be ok running with out it for a minute.
and with out the accessories running, you should be able to hear the noise easier if it isnt an accessory issue
and with out the accessories running, you should be able to hear the noise easier if it isnt an accessory issue