Jim, you mentioned that you were running 10 degrees initial advance; at 3200 - 3400 rpm the centrifugal advance will be all in AND at sustained speeds the vacuum advance would also be in....if you total all of those up I'll bet you are too far advanced at cruising speeds causing detonation.....that could be the cause of the ring damage....normally the TOP half of the rod bearing will show more wear when subjected to detonation and I have seen it severe enough to blacken the rod behind the top half bearing...I'm a bit unclear as to why the top half of the mains showed more wear....perhaps the rotation of the crank forced more oil to the lower half...if thats the case then the volume(not necessarily pressure) was insufficient ...a buck and this information might get us a cup of coffee but it might help diagnose your problem....good luck
