What year block? Is J a year?

[Rob4]

I'm trying to figure what year the block is that I recently acquired. It is a 506 block with the number 12555506 on the driver side of the block at the rear. On the passenger side are the numbers/letter 09 12 J. Isn't this the location for the date the block was made? Does the J represent a year? Am I looking in the wrong place for the date of manufacture? Thanks.

[merlot566jka]

here is a long stretch, but gm used letters to identify ears in the vin code. J would represent 88 in the vin.

now if that applies to blocks too, I would be surprised

[john8662]

According to my cheat sheet (info collected on these very forums), it's a 2002 6.5 Block.

J = 2002

J Dub

[Rob4]

I measured the bore. It must be a 6.2. I guess the J makes it a 1988. It has a 2004 IP but probably been replaced. It came from the military if that means anything. Thanks guys for your input.

[john8662]

6.5 = 4.054"

a *506 is always going to be a 6.5L, the question was what year...

[Robyn]

Whats the possibility that this block was a Military block.

I have seen some wierd stuff in the MILSPEC engines