Here is what you should do,
Get yourself a crayola-cran, I like yellow because its easy to see, then color both sides of the ring, put your bearings in, and drop in the crank. Put on the cap, and turn the crank around 1 time. Then pull the crank out. Look inside the block at the rear seal area and see if you see any yellow, if so your clearance is not enough.
The crayola-cran method works because the part that covers this saturn ring is not in a perfect circle. On my block when I looked at the edges of the ring I had lots of clearance, when I did the test it showed I was hitting on the bottom where I couldnt see by eye.
If you dont have enough clearance, there are two things you can do, the best way is to have the crank turned, they can mill down the ring .005 to .010 and this wont effect balancing of the motor. The other is to die grind the block and cap a little, being very careful not to slip. Grinding the block and cap is fairly quick and easy, because its the 90 deg edge that hits so, 5min of work and your finished.
Let us know if this was the problem