The changeover to CFD and Julian daate codes happened in the April/May/June, 62 time frame.
Here are my comments from an email discussion with Verne back in 2013:
Verne,
Nailing down the details on the CFD changeover has been high on my research list for some time and it drives me crazy. There doesn't seem to be any documented history and it's not clear if the W engines were still being cast at Tonawanda only under the CFD label or if production was actually moved to a different, or new foundry within the CFD organization. If it was just an organizational name change, why did Tonawanda continue their small block and later, the big block castings in the ususal form instead of with the CFD logo, and julian dates like the Ws. That leads me to believe that W casting was moved to a different foundry. In fact, the block markings under CFD were near identical to the Buick and Pontiac castings as I recall.
Here is a tantalizing note I found while searching for GM's foundry history:
"1961 - Chevrolet conducted its first ductile iron heat at Chevrolet Grey Iron Foundry in Saginaw, Michigan Chevrolet then built a ductile iron experimental foundry in April 1962 and its first production foundry in November 1962.
1963 - Chevrolet's ductile iron crankshaft becomes GM's first ductile iron production part.
1965 - GM's Central Foundry began producing ductile iron crankshafts at its Danville, Illinois plant.
1965-67 - GM designed and built new ductile iron foundries in Saginaw, Michigan and Defiance, Ohio. "
Note that the ductile iron experimental foundry was built in april 62 which pretty much coincides with the change in castings to CFD, Julian dates, armasteel main caps casting clock and the "X" on the block.
Here's a note I wrote to my file earlier to document my train of thought when I was working on this a few years ago:
One thing that I have always been interested in is when, where, and why the change of casting foundry of the W engines to CFD (Central Foundry Division or Central Foundry Defiance?) in mid 62 along with; the X on the block, Armasteel main caps, julian dates, and the appearance of the casting clock, which seems to be associated with the Saginaw Foundry since it also started appearing on Flint assembled smallblocks around the same time and they were cast at Saginaw. All these changes seem to have occured at the same time, around May/June 62.
What I would like to determine is whether the change actually shifted casting from the Tonawanda Foundry to the Saginaw Gray Iron Foundry (SMCO) or was it simply an organizational change where the Tonawanda Foundry was redesignated as part of the overall GM Central Foundry Division but still located in Tonawanda, NY.
If casting was shifted to Saginaw, which it may have been, then the castings would still have to be shipped to Tonawanda for machining and assembly. That doesn't seem very efficient, but there may be other reasons for the shift.....lightening the workload on Tonawanda in preparation for the Mark IV (396) introduction in 65, or possibly the establishment of the Experimental Castings Foundry, which I discovered in this history of significant Saginaw Foundry (SMCO) events (see attachment).
Note the two interesting events in 1962, namely :
1962 Experimental Foundry Completed
1962 First Nodular iron poured on #15 and #17 conveyors
The appearance of the X on the block and the Armateel main caps might possibly be associated with the establishment of the Experimental Foundry and the Armasteel mains may be nodular iron, which GM was just starting to use in various castings including 283 cranks in 64.
The entry" 1967-Nodular iron plant completed" refers to the completion of a dedicated foundry for nodular iron parts in Defiance, Ohio which was known as Central Foundry Defiance which is also sometimes referred to as CFD. The W engine was out of production by then, so I don't believe CFD as it appears on the 62-65 castings means anything but Central Foundry Division and should not be confused with the later Defiance foundry.
One would think that if W casting was moved from Tonawanda in 62, there would be some written record of the shift, but so far, I haven't been able to find it.
