Stamped letters on rails

2.2 T1 NC block has stamped letters on the rear oil pan rail on the gasket surface. Any idea what they would be for?

Yes they were stamped on the rail to determine what size each cylinder bore was, so the correct piston would be used. ABCD were used in production. Letter E was sold by DC/MP performance. Each letter represented around one third of one thousandths. In other word around .0003. BTW the back of the block was typically also lettered. Many times you can still see the lettering on the block after all the grease and grime are removed.
Todd

Interesting. Thanks.

Naturally the pistons are also stamped to allow select fitting of pistons/bores.

Thanks
Randy