So what kind of performance boost can you expect? Every processor is unique, and the overclocking potential of one Core i7 4770K isn't necessarily identical to another. It can even differ by a couple hundred MHz. There are 4770K CPUs that achieve 4.8 GHz with air cooling, while others don't get further than 4.3 GHz. So there's a lot of luck involved, which is only part of the fun of overclocking.
We tested a retail Core i7 4770K combined with a Gigabyte Z87X-UD3H motherboard, 2x 4GB Kingston HyperX Predator 2666MHz modules and a Noctua NH-U14S cooler with two Corsair fan. Once we set it to 1.2V we managed to increase the multiplier to 45x, making the CPU run at 4.5 GHz. That resulted in a Cinebench 11.5 score of 9.71 points, which is about 20 percent more than the 8.08 points of the not-overclocked 4770K.
4.6 GHz resulted in repeated freezing of the system within a few dozen seconds of Prime95. When we increased the voltage in steps of 0.01V the stability improved, but it wasn't until 1.25V that 4.6 GHz became truly stable. At this point we were pushing the limits of our air cooling. Most of the time the temperature was just below 90 degrees, but there were peaks up to 92 degrees.
Increasing the baseclock wasn't possible. With a 1.25V Core voltage, 101 MHz bClk with multiplier 46x wasn't stable. When we increased the voltage to 1.27V, CPU became to hot so we halted our attempts.
In the end, with 4.6 GHz we achieve a Cinebench 11.54 score of 10.1 points, which is 25 percent more than the stock performance.
We ended up with 46 x 100 MHz = 4.6 GHz and a Cinebench score of 10.01.