I have a 97 Civic coupe with a Y7. Previous owner claims he changed the timing belt. If for some reason the cam gear was not set to "UP", could I set the engine to TDC, loosen the tensioner, slip the belt off, adjust the cam, slide the belt back on and tighten the tensioner again? I tried searching but couldn't find a definitive answer.

 

Yes, however, if your ignition timing isn't off, then your mechanical timing isn't out.

Have you thrown a timing light on it to check your ignition timing?