what are you overclocking to? use bois and turn off cool n quiet. get a 30$ cooler then overclock. go to overclockers.com to get your understanding of phenom 2 overclocking. Im at 3.8 on 1.4 volts but my motherboard sucks, it could be lower.
Whether you are using the stock cooler or an aftermarket one, do the same thing:
Run the internal multiplier up as far as you can, increase the core voltage if you need to, monitor the core temps, and stop when you reach the suggested thermal limits.