3.8 GHz on ES Ryzen 7 1700 samples require 1.25000V, which is the average for reviewers, possible on the stock cooler. However, it seems like these were cherry picked. Most Ryzen 7 1700/1700X/1800X needs about 1.275V at that clock.
The stock cooler may be still alright for that voltage. I suggest going for 3.6 GHz (stock 1800X) clocks first. Try a VCore of 1.25000V and Multiplier Ratio of 36.00x BCLK: 100.00 MHz.
If you are lucky the stock cooler may get you 3.8 GHz at multi 38.00x, BCLK 100.00 MHz, VCore 1.30000V.