OK. Just wanted to be certain that you had access to the BIOS.
Download Prime95 for stress testing. That will load the cores to 100% to test for stability and drive the core temps to max. Use a program like CoreTemps to monitor the CPU temperatures.
Core2 Overclocking Guide (generic guide)http://www.tomshardware.co.uk/forum/259899-11-core-overclocking-guide
If you are going to use the stock heatsink, you will not be able to increase the voltage much. So go into the BIOS and start increasing the FSB freq 10 MHz at a time, then testing for stability and temperature. You will be able to do this 3, maybe 4 times, before stress testing fails. Check your temperatures. If your temperatures are below about 70 C, increase the vcore voltage about .05 volts.
Keep working back and forth between FSB freq and vcore while keeping your load temps below 70 C until you have gone as far as you can.