Have a 97 Jeep Grand Cherokee Limited, 5.2L 318 V8. When I tore it down I noticed that each piston is stamped with a letter (A - D). I then noticed that the block mounting surface for the oil pan is also stamped with a letter (A - D) for each cylinder. In the OEM service manual there is mention about the letters and the min/max size for the pistons and cylinders. Although the original owner and the second owner, my friend, say the engine has never been overhauled, here's my cylinder breakdown:

1. cylinder D piston B
2. cylinder B piston D
3. cylinder A piston Blank - This is one of two that broke. The used piston I got is a C
4. cylinder B piston B - This is the other that broke. The used piston I got is a D
5. cylinder B piston B
6. cylinder B piston blank
7. cylinder B piston B
8. cylinder B piston blank

A retired factory worker said they would take the rough cast block and do a "gang" bore and then a "Piston fitter" would do a final bore (?) and fit the pistons. Never heard of such a thing. So how do others tackle this miss-mash of pistons and cylinders during overhaul?

 

It is the same basic idea as if you stamped your rods with numbers...
That piston rod Combo is for that cylinder....
The retired guys is "On the Spot"... the newer production line block are known to have what is called "Core Shift" when casted and this is just one way of keeping things in order...

 

on the old 392 hemis. i found that the pan rail had "A" and "B". i was told by a 392 hemi expert that the letters was the piston size. i think in increments of .000x my 1967 dart, charger factory service manual. it shows the 426 hemi pistons. sizes from A to E. "A" = 4.24975, "B" = 4.25025 i am not sure that you can buy the pistons over the counter in those increment. i ran across a 1972 440 with .010 over pistons. but could not buy them from chrysler.