What are these marks on my block? (~20s Lycoming K)

[Nate Dort]

I have 4 different Lycoming K engines from my collection of Dort parts, spanning 1918 ~1922. Of the three I've examined closely, two of them have stampings under the side valve spring cover, below the springs, that seem to convey some sort of information about the individual cylinders.

 

From the ~'21 block, L to R (Cylinders 4-3-2-1) read "514   514   514   5145":

 

 

 

An older block, circa 1920, has the following stamps in the same positions: "+5   +5    +5     0"

 

The earliest one has no stampings. I haven't pulled the cover off the '22 yet.

 

What do these mean? Some sort of measurement, I assume, but I'm not sure what they would correspond to. The bore and stroke on all of these is 3-1/2" x 5".

 

On a side note, it's interesting seeing all of the slight differences between these engines as refinements were made over the years.