The Max Non Turbo Boost Ratio depends on the type of CPU. 34x is the maximum for the i7 2600K (aka 3.4 GHz). You will need to increase the Core Max Multiplier (range 35 up to 50) for overclocking your system.The Intel doc http://downloadmirror.intel.com/19482/eng/DP67BG_PerfTuningGuide01.pdf gives detailed instructions how to do that. If you have good cooling 45x should easily be achievable, but every CPU is different.
My DZ68BC board has a BIOS option to auto overclock to a maximum of 45x and also increases automatically all other required settings. If your BIOS has the same option you could try this as an easy first step.