Engine Date

What does this date on top of the engine mean and the D and N mean?

 

My guess is that is the date the intake manifold was cast at the foundry. The D and N are likely foundry shift codes, and the teardrop shape likely indicates the shift.
-Donny

 

I would guess that's a date too, but seems odd considering the OP's user name. It's kinda not on the engine; instead it's on the manifold, which would have been cast separately and assembled to the engine as a part.

Agree about the foundry marks. The notion that's a shift indicator is interesting, and new to me. The casting should have a Jeep PN, like 8127342. This is the correct part number for a '77 dual throat V8 manifold. If you see this number cast-in to the manifold, it is indeed from 1977.

 

I have the same markings on the intake manifold of my 1975 vintage 232. I suspect the D/N stands for Day or Night shift, and the date it was poured. Beside the engine block, where they stamped the date code right on it after completion, this is the only date I can find anywhere on the engine.

FWIW: The 232 manifold may have the same date code, but we do not have a firing order cast into ours. Maybe it is unique to that engine line?

 

Tim, The guy I bought my machine tools from worked for GM from '46 through around '88 when he retired from executive level management. He worked his way up from a line worker and foundry, got an engineering degree which put him into R&D. I worked with him for about 5 years, trying to learn as much as I could from him. He explained all the details of GM's casting processes and how to read all the marks on GM blocks. GM sometimes cast parts for other manufacturers including AMC, so some of the marks carry over. I have an AMC block cast with CF (Central Foundry- one of GM's main foundries). GM usually used a "time clock" with a tear drop pointing to the time/shift, so I am surmising this intake above used the same pointer. I can't confirm, but it may be likely Jeff is correct about the D and N.
The numbers cast into the blocks all mean something. My friend showed me how to pick the best (Chevy) blocks to build, not only the obvious 4 bolt mains, but how to determing the high-nickel iron used in select heavy or high performance applications (look for both the "010" and "020" behind the timing chain on small and big blocks)
I wish I could remember all the stuff he tried to pass along to me over those years!
-Donny