Dan - Let's get a little more info on your operation and maintenance of these engines.
What is there standard operating RPM?
What percentage of time are they under load?
What exact engine oil and viscosity are you using?
Do you by chance know what there average operating temperature is of the coolant and engine oil?
What is your oil analysis schedule? In other words, how many hours of operation between test.
Do you change oil based on UOA for extended drain intervals or by a specific time.
If you can, can you email me a scan of the UOA that showed the CU of 65? If so, send it to sales@trclubricants.com and I'll look it over. If you can also send one or two previous UOA's also that would be great. That will give me somewhat of a baseline to gauge that analysis.
The UOA that showed a CU of 65 would have thrown warning light's off in my head. I would have probably taken the engine out of service and done a rods and mains check.
Are you running factory Caterpillar oil filters on these engines or are you using a aftermarket filter? Personally I like the Caterpillar filters. I have cut alot of them open over the years to examine and alway's found the Cat filters to have a lar*** surface area (more pleat's) and thicker filter media than most after market filters. Donaldson also makes excellent heavy duty diesel engine filters and has even recently released a extended drain interval oil filter for diesel engines. Might be worth checking out. I alway's suggest buying the best oil filters you can get and in the case of Cat's, the Cat filter is hard to beat.
Look forward to your reply and helping you track down the cause of the failure. Anytime a citty cat makes holes in the side of the block there's something wrong.