2 5/8" Opening for 2' Toilet Flush Valve??

[Beerski]

Hi.
I have a leaky flush valve gasket on a toilet we've had leak-free for 30 years. I've fixed these on other toilets before without problem, but I can't get a new gasket (rubber between valve base and toilet) to seal. I've tried a combination of two beveled gaskets on two different flush valves. No go. All combinations leak. No cracks in toilet...no leakage at mounting bolts.
I do note that opening through the tank for valve actually measures 2 5/8" in diameter. The valve is very loose in the opening.
Is this right?
Should I be using a 3" valve? (not sure the actual opening size required. Is the diameter measured at the valve seat).
Is there such a thing as a 2 1/2" flush valve?
Ideas?
Thanks,
Beerski

 

[Terry]

What brand and model of toilet? Can you post a picture 1000 pixels or less.

 

[Sponsor]

 

[Beerski]

What brand and model of toilet? Can you post a picture 1000 pixels or less.

Hi Terry.
Sorry for not getting back to you on this one. I never received an email advisory, but should have checked in anyway.
After mulling this over we have decided to put in a new TOTO toilet. What was vexing with the old toilet was the fact that the flush valve hole in the toilet tank was literally oval shaped. Never saw that before. Er go,we have a new toilet.
Thanks,
Beerski