No one answered? How high will the board let you set it? I think the only damage from high voltage is heat but I'm no expert here. I just posted a question about my A7V running a core voltage of (according to MBM) 1.89 although the jumper is set for 1.80.
The highest the A7V goes without modification is 1.85 but I think the Abit goes higher.
The AMD spec for ABSOLUTE MAX CONDITIONS is "max OPERATING voltage + 0.5V" which is the same as 1.85V +0.5V = 2.35V. For overclocking, if you can handle the resulting heat, I wouldn't go any higher than half the 0.5V adder or 2.10V .
I have a 1.1GHz TBird but plan to try lower Vcore for overclocking 1st since some have made it work and it will also help keep temps down since power formula is c*(V*V)*f where c is a constant, V = voltage, and f = freq. Since V is a squared function, going from 1.85V to 1.65V saves 20% in power (heat)!
In additon to heat, and to blowing up the chip by using really high voltages (e.g. 2.5 or more) there is a danger that's called "Electromigration", which ultimately can wear out certain areas on the chip and thus reduce lifetime. Not too much to worry though, since the chips will run for at least 10 years under normal conditions Electromigration may reduce it to 5, which still is ages in the context of this hobby (I think the fastes processor 5 years ago was a P1 233 or so...)