My fresh rebuild was really leaking bad, and now that it's torn apart again, it appears that the main reason for the leak was a warped rear-main seal retainer.

The strange thing is, I also found that the rear main journal has two groves in it that run all the way around. They're spaced about 1/4 inch apart and definitely look deliberate, like there were intended for some purpose (for what reason, I don't know). I'm now wondering if groves were part of the problem. I have a new neoprene seal is going in, but will those groves hamper the operation of the seal? Has anyone see these groves before, or have any experience with this situation?

Thanks in advance for you help,

Ed

P.S. This crank was machined, and why that surface was not turned down to eliminate the groves, I have no idea. The groves may have been too deep.