Long story short...

I tore apart an AMC 360 that I got with a vehicle, no knowledge of its history.

When I started to dismantle it I noticed that it was very clean inside But then I took the heads off I noticed that the cylinder walls were well worn but there was no ring ridge at all. I thought that seemed a little strange, but OK. When I took the stock, standard bore, pistons out I found that every top ring was broken, every one . The second rings were fine. The main/rod bearings had a date of '99 and I believe this engine is a '74 so someone has been in there before.

So, school me:

I don't see marks were someone used a ridge reamer so, why is there no ridge?

And, more importantly, what the heck broke every top piston ring if there is no sign of a ring ridge?


Marks on the cylinder walls are from me using a snap gauge.