I am researching the engine in my 69 Camaro Z28 RS. Next to the Date stamp Code, there is another stamp. See attached picture.

Thanks in advance!

From what I understand, Day shift, Night shift and Third shift.

Cheers,

ZZMike

ZZMike,

Thanks very much. This is consistent with the Date Stamp Code, which shows the engine was forged the second hour of the "first shift." This TDN Stamp must have been added later, because the center of the Date Stamp Code was used to indicate shift. Specifically, a flat head screw in the center meant 1st shift and a round head screw indicated second shift according to Chevrolet by the Numbers. Perhaps this new stamp was added when they went to 3 shifts? Do you know when that was? Also, my reading is that this coding was done at the Saginaw plant only. Does that match your understanding?

Best,

jmcbeth

Relatively, yes. I am under the impression that the screw head on the time indicator was not an indicator of shift, when a "D-N-T" shift indicator was used. As far as I'm aware, this was a Saginaw thing.

Cheers,

ZZMike

ZZMike,

Mystery solved. Thanks for your help!

Best,

jmcbeth