I'll be nice because all I did was steal someone elses voltages when I first got my e8400.
I set Vcore to 1.4 and FSB to 445, multi at 9.0
Stable 4ghz overclock in Orthos for over 12 hours and then I stopped it. Any lower voltage and it was unstable due to Vdroop. Your motherboard may be a little different, but start there.