It is true you should check for valve clearance after having the head machined, but on this type of engine, there should be no need to worry. If it was a racing engine, I would worry. A few thousands here or there is not going to change much, heck the new gasket is probably thicker then the originals. You sure don't want to cut anymore then needed to clean up valve seats. Cut to deep and the next rebuild will require new seats installed which means big money.
Joe
