Hi, I have a 2600k and a Noctua NH-D14 in my HAF 932 case. Heating isn't the issue, voltage is. Here's the thing: I set my CPU voltage in the BIOS as 1.480 volts in order to achieve stability at 4.8GHz, but I then boot into windows, and CPU-Z says my core voltage is between 1.360 and 1.378. Which voltage is the accurate one? Also, will keeping the voltage and clocks at these levels kill my processor if i run the clocks 24/7, even with my D14 cooling it?
Personally, I wouldn't set my voltage that high. With that voltage setting, you should hit the 5GHz mark. To get a stable 4.8GHz overclock, you really only need 1.385 to 1.4 volts. Every CPU is different, but the voltage drop your getting could be telling you that you don't need the 1.480 volts your trying to give it.
If you're really set on the 4.8GHz, I would set your voltage to 1.4, then run Prime95 for 12-hours or so and see if it's stable. If stable, then your good-to-go. Just as a warning, you'll probably hit 70C or slightly above during the test, so if you're ok with that, then go for it.
I've been able to get my 2600k @ 1.5 volts up to 5.0GHz stable. During Prime95, temps reach in the high 70's, so I settled for 4.2GHz at stock voltage (1.215), which I reach about 60C average at full load.