Strange time for this to come up. I got a motor in yesterday for a core that the owner was having to constantly put oil in but never had a serious puddle. I began dismantling it to find the babbitt having voids, some as large as a pencil eraser. The first thing I found was a felt ring stuffed into the oil cap that was saturated with oil thus creating a plug for the oil fill and the crankcase. When this is done as the pistons rise they pull air into the crankcase via the rear tube and slinger. As the piston move down, this excess air is compressed and expelled via the same route except now the oil has to be pushed out first creating a terrible leak even with a good main and correct clearances. It also had a Burtz seal which along with being not much good in my opinion, had failed because of so many adverse pressures working against it. I also found, completely by chance, the return tube had been powder coated and either the ends were plugged with cloth then to keep powder out or, later to stop oil flow which, it did quite effectively.
Just some things to keep in your mental register for use later. If it can be done, it will and wrong sometimes.
