Meaning of markings on the back of an engine block for 1936 Cadillac

Question:

l am rebuilding the V-8 for my 1936 Cadillac and came across some markings on the engine block that aroused my curiosity. There are different letters stamped into the top of the block next to each cylinder. Can you tell me what these letters signify?

Answer:

Discovering and investigating subtleties such as the markings in your engine block are among the many things that make our hobby so challenging and enjoyable.

The letters stamped into your engine on the top face of the block adjacent to each cylinder were put there by the factory to denote the exact diameter of that cylinder. Each of the original factory pistons was also marked with a letter that corresponded to its’ exact diameter.

These code letters enabled the factory to selectively fit the proper size piston to each cylinder, resulting in uniformly tight tolerances in spite of inevitable production variations relating to the diameter of the cylinder bores and pistons.