Overclocking on the Z370 platform is pretty much the same as Z270. You’ll just need to set your BCLK and CPU core ratio. The only real issue with this platform right now is that these chips get hot, real hot! For those who are new to overclocking ASUS has a 5 GHz OC profile you can simply just load.
If you wanted to manually overclock in the BIOS yourself just set the BCLK frequency to 100.00, the CPU Core Ratio to Sync all Cores and then the ratio you want. We are shooting for 5.0 GHz on our Core i7-8700K so we set it at 50.
You are probably going to want to set your own CPU voltage (Vcore) as well. If you have it set on auto it is going to want to push more voltage to the CPU, which will result in higher CPU temperatures. We set ours at 1.30V.
So 5.0 GHz was a stable overclock, but barely. Our cooling solution was a NZXT Kraken X52, which is a pretty great AiO, but running benchmarks or our stability test our CPU temperature was around 90C, which is a little scary. Of course de-lidding your CPU and using liquid metal could help with temperatures, but if you plan on running a 24/7 overclock on a Core i7-8700K you are going to need some serious cooling.