Emergency AD Affects TCM Lifters
Anyone who's bought a new Continental engine, had theirs rebuilt or had top end work done since June 19, 2009 could be affected by an emergency AD requiring replacement of the hydraulic lifters installed in those engines. There have been at least three cases in which the lifters wore out in as little as five hours. Teledyne Continental Motors issued a mandatory service bulletin (PDF) Nov. 3 and the FAA issued the emergency AD after assessing the MSB. The AD includes part numbers 657913, 657915, or 657916, in Model 240, 360, 470 and 520 engines. Although 550-series engines are not mentioned in the AD, there are reports that they are also affected. The lifter problems have also delayed rebuilds that were on the bench when the problems became known.
AVweb heard from at least two owners whose rebuilds were stopped because lifters weren't available. It's not clear when the supply of lifters will return to normal.