What is the likely source of this aluminum?

The O-540 in our Pathfinder was making metal at the pre-buy inspection. It
turned out to be aluminum from the piston pin plugs, and the amounts we
found convinced us to slash our purchase offer, and put in a new engine when
it was accepted.

(BTW: The new piston plugs are made of a harder alloy that won't spall,
supposedly.)

If you found a "few slivers" that's not abnormal. If there are a lot of
slivers, and you're flying a C-172 with the H2AD engine, you may have some
serious trouble brewing. (That engine was known for making metal, although
the latest oil additives supposedly have alleviated this problem.)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"