What CPU cooler are you running? I am on stock atm, but want to OC my 1600.
NZXT Kraken X31 but its complete overkill, even stress testing at 3.9Ghz+ its only reaching 55c with silent fans.
You should be able to get to 3.7 or 3.8 on the box cooler, an inexpensive cooler like this will easily get you as far as it will go. https://www.overclockers.co.uk/alpenfohn-ben-nevis-cpu-cooler-120mm-hs-048-al.html