It Is from the rough stage of machining of the block for lifter holes for clearance. so final tooling to bore and finish valve train lifter bores ..
Retired form Chrysler Trenton Engine plant ..Seen a lot of them..
Ok thank you
This is a 72 model block
I have a 68 - 70 - (2) 74 model blocks all trucks blocks like this one and none have this machining so was just curious.
