Although Lycoming says at least 1300 of its own engines are affected by the SB and now AD, the FAA AD language says 778 airplanes on the U.S. registry are covered. The FAA estimates the total cost of the AD to U.S. owners to be $1.1 million or about $1425 per engine if no replacements are required. If connecting rod replacement or bushing replacement is required, the cost ranges from $2170 for four-cylinder engines to $6680 for six-cylinder engines. The FAA said it believes the bushing issue represents a serious enough safety hazard to short-circuit the usual commenting period for ADs. Here's the proposed text of the AD. As of Wednesday, it was unclear how many of the named engines are Lycoming factory engines and how many are field shop engines. For more, see Lycoming's FAQ on SB 632.
This is a companion discussion topic for the original entry at https://www.avweb.com/ownership/faa-proposes-emergency-ad-for-lycoming-rods