I stand corrected, I should have done the search before replying... A
couple-three years back when the Continental crankshaft failures were
the topic of discussion I had done an AD search on Lycoming crankshafts
(since a have a pair of them) and the FAA web site did not show any for
Lycoming since the early 70's... I hadn't repeated the search
recently... My bad...

But, the topic of metallurgy failures is not limited to Lycoming and
Continental... Both Superior and ECI has massive recalls on cylinders
for early wear and cracking, including failures in flight...
Continental big bores are famous for the rocker arm bushings wearing
out every 900 hours (I've been through a couple of early top overhauls
over this)...
Lycoming parallel valve cylinders are famous for lack of cooling oil to
the valve stems leading to morning sickness (been there, done that,
got the tee shirt, now I use AVBLEND)...

The problem is more than just Lyconsaurus being dinosauers... Airplane
engines are highly stressed machinery... If they were engines pumping
water from the mines, or turning dynomotors for municipal electric
plants, or pushing 900 foot container ships, we would just make the
parts so heavy and thick they could never fail, but that is not an
option with airplanes.. It seems that every major player in the
aircraft engine market has been bitten by the metallurgy bug... Is it
the stress on the engine parts, or the FAA regs, or bad metallurgy? I
don't know the answers but there do not appear to be simple
solutions... Every company producing engines/parts has bright people
working for them, so if there were solutions they would have been
implemented and we would not be having this discussion...

denny