Intel i7 2600k vcore problem.

OK, I have an OCd 2600k and I use cpu-z to read Vcore, Core Temp for core temps and prime95 for testing. How did you OC. Did you use auto Vcore or offset? Auto will overvolt to ensure stability whereas with offset you have options. You can also use manual if you want.

Using an offset of 0 (stock voltage) you should get 4.2, so at 4.0, you can undervolt a bit. Remember after each boot to run the 3 programs I mentioned. If you are at a comfortable frequency, then keep trying lower and lower voltages.

Doing this should yield 4.0 at offset -0.02. If you need more than stock voltage you either have a bad chip or a cheap mobo or PSU. Hope this helps