'Splain this to me - H2AD question

[rjcthree]

I've torn down my core, a first run O-320- H2AD(2058TTSN, NDH, never opened, EXCELLENT logs), and been mostly very happy with what I found. Since the H2AD has a checkered past, I requested and was provided the pre-purchase inspection of the aircraft, as well as another inspection of the lifters. Both were CLEAN to the point of almost convincing me to put a couple hundred hours on it before I OH'd it.

GOOD THING I DIDN'T.

Lifters look great. No spalling, abnormal wear. The cam is not so nice, one lobe , about 2/3 across the center of the lobe tip, has spalled. Little material had actually been removed, but scratching with a fingernail removed a patch of material about 1/4" wide by 1/16" across. Yikes. Nothing in the screen, I haven't cut the filter yet, no abnormalities in oil analysis reported.

I was advised to turn the cam into a nice lamp.

So the question: How is an engine known to eat LIFTERS eating cam?

Everything is going out for tagging, so hopefully there's no more gremlins in the works. Bearings all look used, the rod bearings look well-used, wear patterns generally even. Journals look good, I'm expecting only polishing (based on my past engine building exp, which is 15 years gone by!)

Crank/rods/gears all going to AES in TX, case going to Crankcase Services in OK. Both seem to be completely professional folks - and even nice to talk to.

Rick 90432

[mahlon_r]

"How is an engine known to eat LIFTERS eating cam?"
It is known for eating both... You can't have one without the other.
I think you got to it at a very early phase of the process and are seeing the beginning of the cam and tappet face self destructing or someone installed new lifters recently.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

[rjcthree]

Mahlon, thanks for your reply. It was my understanding that the lifters failed first, hence the 'lifter inspection' requirement, and general practice. The logs are really good, and no mention of the lifters being replaced exist. The PN's on the lifters are all obsolete, so I believe them to be original - but who knows?

Either way the cam is scrap metal, and the lifters are on the 'replace at overhaul' list. The $1000 hurts my feelings, but not nearly as much as the funny shaped stick in front stopping unexpectedly would!

Rick

[osxuser]

If I buy a core lycoming, I PLAN on putting a new cam in it, as well as new cylinders. Everything else gets sent out.