This is a fairly old report that I came across today and it rang home with me.
I have had to rebuild my RV 3 engine due to corrosion issues in the crankshaft.
The engine is a O-235-F2B of 125 hp with an inverted system.
The first maintenance task a week after purchase was to pull the engine to repair a crack in the engine mount. It was quite a surprise when I undid the down pipe from the Tee piece of the inverted system to find it was full of water. After the engine mount repair I undid this hose at every 25 hour oil change and it was usually fairly full of water. At the next annual I pulled the crankshaft plug and found the crankshaft was beyond repair.
My opinion and only my opinion is that the metal Tee piece is acting like a condenser and dropping water down the inverted pick up hose.
My type of flying is only occasionally sportsman aeros usually +ve G. If the aircraft had been flown in hard aero's then this would not be so much of a problem.
For my flying I removed the inverted system to stop moisture build up.
So my advice is if you have a inverted system remove the drain pipe at every oil change to remove the water.
L4 Cub Share
RV8 in very very slow build