Hi relatively new to the forum. Engine is a replacement for my truck. Checked piston stroke with screwdriver through spark plug hole and it is ~4”, so it is a 400. Numbers stamped on my engine block : D7TE-A3B, date 7M15.
I have done some searches through the forums, and I see that the date code letter should correspond to a month. In my case my date is M. What does that mean? Last I checked, there aren’t 13 months… So I am thinking maybe January 15, 1978 or something?

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From what I gather on casting dates, Ford DID NOT use the letter I, and M would be December. Thinking I here could be confused with 1. Are we seeing a hole in the block?

D7TE would be D=1970's, 7= the year. 1977 engine block

 

Thanks, iicap! I was suspecting maybe skipping the “I” to not be confused after I mulled over my post. Do you mean what looks like a hole at the bottom left? I think it is just an optical illusion in the photo. I think that is shadow from the contoured casting going to the engine mount from what I remember in reality.