Where are the timing marks on the gears? Im trying to replace the timing belt? on 2001 Toyota Sienna

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The car will not pass smog. There are 167k miles on the car, and i do not believe the timing belt has been replaced with the possibility the belt has stretched and advanced the timing. Any suggestions?
(2) Answers
If you get a factory toyota timing belt , the belt is marked for where it matches up to the cam and crank marks. Service manual (even haynes or chiltons) may be handy to help with visualizing the marks and set-up. And , no the belt will 'wear' but not 'stretch' it's fibreglass cord. Before blowing money on the timing belt , have the rest of it looked over for EMISSIONS related problems. Performance and emissions do not necessarily go hand-in-hand.You can have a great running engine with a bad converter fail , and a very poorly running engine with all emissions controls (working their butts off) pass.Diagnosis will be a money saver, if you can find an emissions specialist in your area.
take the number one spark plug out and turn the crank until you get to top dead center Iassume you have the timing cover off if your at tdc then there should be a mark on the cam and crank gears