There are quite a few different ways to overclock on the Fatal1ty Z170 Gaming K6+. The easiest way is to use the F-Stream software and select auto tuning. This will give you the best overclock based on your cooling setup. After running auto tuning it gave us an overclock of 4.34 GHz, which was pretty weak in my opinion.
You also have the ability to Load an optimized CPU OC setting in the F-Stream software. Now remember these are not guaranteed to always work.
You can go into the OC Tweaker section of F-Stream of the BIOS and fine-tune yourself. That is what I did and I came up with a stable overclock of 4.7 GHz with a Vcore of 1.35V.
It seems 4.7 GHz is the highest stable overclock current setup can handle as most Z170 boards we have tested have maxed out at that speed.