Wow, this is the most asked question I think ever.
You don't adjust tolerances, these engines use hydraulic lash adjusters, which automatically adjust themselves. The oil passages in the rocker arms get clogged with sludge, and no oil gets to the HLA's, therefore they tick. A rattle may be something else though. Anyway, I've had decent luck with an engine flush, other people suggest an additive like Marvel Mystery Oil, or Rislone. The best thing, but, most expensive, would be to replace all the HLA's, but, they're like $25 a piece from the dealer, and it takes 12 of them.
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