Edit 1 - If anyone is interested in how the GPU performs while water cooled, this is the Strix 1080 A8G model running 100% of the time at 2088 mhz, without me having to touch any sliders in software. This must be due to the built in boost algorithm allowing it to reach that clock speed without any thermal throttling (instantaneous max 56 C).
This build was mostly a learning experience, but also a migration of parts from an earlier build that were in my Enthoo Evolv mini-ITX case. This time around, after I had already owned the s340 case for a little while, I decided I wanted to try my hand at constructing my first fully custom water loop.
Trying to find space inside this case for a custom loop of more than one component was difficult, mainly because it only has one location for radiators larger than a single fan in length. Regardless, the idea was to have a 240 out in front followed by a 120 against the back. Trying to install soft tubing for the very short runs from the 120 to the CPU ended up being very difficult combined with my lack of experience.
After days of planning, purchasing, cutting and building, I thought I was finally done putting it all together, so I started stress testing the CPU. As soon as the temperature in the loop rose, coolant started to slowly push its way out of every possible crevice on the CPU block. At that point, I was demotivated, and didn't really have much time left to complete the project I started. The culprit for the faulty CPU block was probably my janky installation skills, because at one point I found myself using way too much awkwardly applied force to seal tubing onto the fittings, fittings onto block, etc. Oh well, valuable lesson learned for the future.
With no patience left, I just ended up taking the Kraken x42 I already owned and rigged it to fit at the top of the s340 so I could start using my PC again. The top is not designed for both a fan and a radiator, so I had to use a 120mm fan on the 140mm rad and mount the fan off center to gain clearance around the fan headers and the kraken pump housing. Remember, when mounting points are not there, 3M adhesive is your friend.
As for custom cooling, I reverted my work back to a state that worked flawlessly the first time, the GPU in a loop by itself. These are all EKWB parts, and I think the final result is pleasing both visually and with its performance. Temps rarely top 50 C on the 1080 (and 55 C on the 6600k) with constant-slow-speed fans. My two goals for the loop were eliminating noise from stock GPU air coolers and dropping temps at the same time, both of which were achieved. The price for the loop reflected on the parts list includes the CPU loop components as well, because maybe one day I will revisit this project and actually complete it. For now, I think it looks pretty good, all things considered.
And yes, I'm aware there is no drain in my loop, that is also something I learned the hard way (having to drain it multiple times to study the leaks), and I'm also aware I left the sticker on the Kraken rad.