They all click. It's called "solid lifters". You *could*
spend the money on a valve adjustment, but it'll run like this
for anothre 100K, so why bother?
You could be hearing piston slap, but I think you would have
said that it goes "tocktocktocktock" when it's cold especially...
and also, while that's a bit more annoying, doesn't have much
effect on longevity either.
Next time you replace the valve cover gasket, you can check the
valve clearances and see if any are way out of whack. Then decide
if it's worth fiddling with it.
Have fun!
===
Rob Bareiss, New London, CT ::: 86 244DL, 87 244DL, 88 744GLE, 625K Total