Do V6 Toyota valves tighten when wearing?

Do V6 Toyota valves tighten when wearing? Well first of all - one has to determine what exactly your question means. Do valves tighten? I have to assume you mean does the valve lash diminish. So I am guessing you are asking that when valve and seat face surfaces wear - does the lifter gap (or lash) get smaller (or diminish). The answer is no. First off - valve and seat face wear is very very minimal. Any wear that could occur here is exceeded by the wear to the lifter/shim/valve stem end. Most experienced technicians will tell you that no adjustment or shim replacement should ever be necessary. That is correct. Unless you have extreme case like trying to get half a million miles out of the engine.

If valve seats were ever replaced, and the inserts were not completely seated at installation, then the lash could diminish over time as the seats fully bottomed in the bores. But you never presented that as the case.