The FAA has issued a Special Airworthiness Information Bulletin concerning fatigue cracks showing up in some ECi cylinders on Continental engines.
The bulletin recommends inspecting ECi cylinder assemblies that have logged more than 500 hours on Continental 520 and 550 series engines. It suggests inspecting them every 50 hours, looking for cylinder wall fatigue cracks which show up near the exhaust valve seats. The bulletin recommends standard compression and soapy water tests, as the result of the cracking is decreased compression and leaks around the valves. The 50-hour inspections fit nicely with oil changes, the bulletin notes helpfully.
These cracks started showing up three years ago. They have appeared after a little as 253 hours and as much as 1,489 hours, according to the FAA, which adds that the bulletin is offering recommendations, which are not mandatory.