I overclocked mine a piece of cake straight out of the box to 3.7ghz on stock volts, I then raised the voltage and went to 3.9, took the voltage upto 1.360v in total.
Trying for 4ghz just needed so much more voltage and generated so much more heat, it wasn't worth it for an extra 100mhz, most of the time overheating VRMs were crashing the computer, complete power off.
Running it on a Gigabyte AB350m Gaming 3 with 16gb G.skill Trident Z 3000mhz, Geekbench 3 score 3942 single core and 31537 multicore, at that's with my RAM at 2133mhz instead of 3000mhz.