I have a Lian Li Lancool 170M Tempered Glass MATX case and am trying to find a AIO that will fit in the mount on the back of the case, which is a little tricky because it is small.
Sorry, no, there are no 80mm AIO on the market. That is not enough radiator surface space.
The specs say there are two places for 120mm fans in the front, perhaps you could put one there? But the specs specifically say not ready for liquid cooling, so there probably isn't clearance. You would probably need to discard the front panel and that would look terrible. The short version is that when the specs of that case say no to liquid cooling, it means no.
TitanRig used to sell 80mm radiators so you could have put together a custom loop, and maybe you can still find a seller that has them. But it would not have much cooling power while being expensive. I highly recommend you don't.
Two 80mm segments is less radiator surface area than a single 120mm segment:
And a 120mm AIO can barely cool a modern CPU, even a lower end model.
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