I noticed these three casting marks on the deck of my mid-year 1924 block and was wondering if anyone knows what they mean.
The number "3" is by the valves between cylinders one and two.
The number "6" is in between cylinders two and three.
The letter "W" (or "M")is near cylinder four.
They're stamped by inspectors at various points in the machining/assembly process. What they mean to you, is that the block has never been decked.
I just realized that I posted this in the wrong section.