warm?

i always adjust mine cold.  0.008" intake and 0.012" exhaust.

as for the clatter.  if you over tighten your valve cover it will pull the rocker assembley up , loosening the rockers causeing them to clatter.

also you may want to pull the cover and check to make sure none of your adjusted lock nuts didn't come loose.

it is normal for them to make a little noise though.  if you adjusted them right then don't worry about it.