On 2008-03-24, Robert Moore wrote:
The "H" engine was one of Lycoming's worst products, bad camshaft material.
Numerous failures early in it's life with the resulant FAA Airworthiness
Directive requiring a special oil additive. Pretty much a non-issue now
since most major oils have this additive as standard.

Some wags said the -H2AD was Lycoming's way of telling pilots it'd have lots
of ADs.
--
Jay Maynard, K5ZC http://www.conmicro.com
http://jmaynard.livejournal.com http://www.tronguy.net
Fairmont, MN (FRM) (Yes, that's me!)
AMD Zodiac CH601XLi N55ZC (ordered 17 March, delivery 2 June)