[H. L. Chauvin]

Per part of comment in reply #6:

"Did you ensure the pistons were re-installed in the same hole they came out of?"

Whether this was the primary cause or not, in re-installing pistons and connecting rods, we are involved with measurements in thousandths of an inch; former engine cylinder/ring wear; and human beings performing the initial re-bore of the block where all cylinders may not be 100% "exactly" alike.

FWIW: Always a good idea to provide small marks on tops of pistons and sides of connecting rods, e.g., from I thru IV on piston tops, and small l, ll, lll, llll, vee marks on sides of connecting rods.

Mechanical failures always occur for a definite reason:

If you would have had several "shop" spy cameras rigged up in your shop, you could re-play the video and possibly "see" the actual cause of the wear ..... maybe not enough water replaced in radiator or whatever ..... "hint", "hint" .... we might have to wait until next year for Model A parts suppliers to offer "shop" spy cameras for after-the-fact mechanical investigation.