I was asked to come look at a customer's airplane, they had a cylinder failure. This is on an o-300, but the jug is the same as the 0-200. C-90, and the c-85. Total time was 1400. Pilot landed safely. Compressions were good on the last annual. I dont think any routine inspection would have found this fatigue failure, the barrel actually broke and about 1.5" was still in the head. Since a lot of cub drivers use the small continentals, I thought I would pass this information along. I will be submitting a service difficulty report to the FAA. I hope no one else has to encounter this. Tim