You can't let set a numeric for vcore straight away and get your CPU overclocked and running stable.. My recommendation is to proceed with a step by step approach.. First try keeping the vcore to its default value and increase the FSB in finite steps.. See how far can you push it that way.. Increase the vcore only when you notice any sort of instability.. And even then, increase in very small steps (0.1 or may be even 0.05 depending on how your motherboard allows you to fine tune it).. Remember, one setting need not work for even two similar rigs..
Just play with it. We really can't give you an exact answer, because the number varies based on the individual chip. Two people with i7 950s may get very different results. I have a 1.256vcore i7 930 at 4.0, so that could give you an idea of where to start. If you oc it at that voltage and its stable, just try lowering the voltage slowly until it becomes unstable. You may have to go higher or may be able to go lower than that. It all depends on your chip. DO NOT go above 1.375! That is the intel posted limit for your voltage range. If you go above that voltage, you may start damaging your chip. Also keep track of your temperatures when overclocking using Realtemp. Realtemp is very accurate for tracking temperatures. Many other programs will give you inaccurate numbers. Try to keep your temps under 80C when under load... I personally would never use an overclock that goes above that temperature...
adjust the blck but turn off auto for the vcore voltage. or it will auto over volt when it doesn't need to
in voltage control take it off the auto setting and set it to 1.18125 which is stock or near enough.
you may also want to drop the memory multiplyer to get your memory back to 1600