I don’t think that’s the oil drain back valve. I think it’s the oil bypass valve. It’s been a couple years so I’m sure you’ve figured out the answer since then, but I wouldn’t run it without either of them. The drain back valve being missing would cause somewhat of a dry start, whilst the bypass...
I too am worried about the oil contamination. Im thinking about modifying it a bit to make it stronger, but even then, the temp of the oil is higher than the glass transition of the PLA/PETG… I don’t want to introduce any more foreign objects into this engine than I have to, maybe I’ll try to...
Just broke mine as well, I’m ordering a new oil filter housing. Then I’ll 3d model a new cup and post it online for free. Terrible design, in my opinion. Pandering for money possibly?