Yea.....just make sure you research the max voltage for each chip that should be sent through on air cooling.
For the Conroes and Wolfdales i would say no more than 1.5 should ever be sent through there....thats what i have heard however i wouldn't ever put more than 1.45v through my E6300.
For the Allendales(mainly the 1xxx and 2xxx series) i would say never put more than 1.45v through them but try to keep it as low as possible.
There are two ways to kill your CPU
Too much voltage
Too high temps
both over a period of time (or at once if the voltage or temps are incredibly high) will deteriorate your chip.
Don't let me scare you though becuase to this day i still have not heard even ONCE of a Core 2 Duo just dieing....it just doesn't happen...becuase odds are as baron said your mobo or chip will probably shut down if things even get a bit dangerous.