1.000v as stock will be fine, but yea @ 4ghz mine locks me out too.
1.1v @4ghz is pretty good, I use IntelBurnTest for my OCs and 4.2 ghz gets me 75-77c with 1.2v but IBT stresses harder than prime apparently. I should take the time to lower the volts, but anything under 80 is fine.