Ex58 - ud4p and an core i7 920, how to overclock?

i have mine clocked at 3.8, could go higher, but no need to stress it out, runs at 37 idle and 58 load, ideal!

i have a ud3r with the 920, I haven't gotten mine past 3.8 and that was only stable for about 8 minutes, then BSOD. I have C0 stepping chip, and had my core voltage in the bios set to 1.4 . think my qpi was at 1.3, temps never went above 70. Im not a super braniac with this kinda thing , what other voltages need be adjusted to get 4.0 ? This is a lil weird because at 3.5, it runs nice n cool at 59 under load and 1.27 core voltage. I know im not providing muhc info, but if someone could lend me there exact bios specs , mainly voltages would be awesome. I also have the F3 bios, dunno if it makes a difference , just thought worth mentioning. I do not plan on keeping her at 4ghz, just want to see it happen. thanks alot everyone in advance.