How to identify a block casting date on a stock "numbers matching" GM 6.5 diesel truck without removing or moving anything:
Tools required: Flashlight and a Smartphone.
Time required: 5 minutes first time. ~2 minutes every time after.
Climb under the hood with flashlight in right hand, smartphone in left. Photo 1 is almost exactly where you need to position your tools.
Date code is on the vehicles right side between the heads and the transmission bellhousing.
Date Convention on 6.5 Blocks Cast by GM: MDDY
First digit denotes the month (A=January, B=Feb...)
Second and third digits denote the day (01=First day of the month, 02=Second...)
Fourth digit denotes the year (8=1998, 9=1999...)
C268 indicates March 26th, 1998
Date Convention and Location on Blocks Cast by Others:
Navistar Optimizer blocks use a different date convention but have the code in the same place as GM (excluding P400's).
Not sure what Dalton Foundries or others do. Refer to other sources.
Tools required: Flashlight and a Smartphone.
Time required: 5 minutes first time. ~2 minutes every time after.
- Reach in and feel for the digits, once you do wipe the dust off so they are legible. Put a bit of clean oil on your finger and brush it over the numbers to make it really stand out in contrast to the rest of the dusty surface.
- Figure out how to focus your camera (most phones you just tap on an area on the screen that is in the same depth of field as the digits you want to read.
- Flashlights with a focusable lens (adjustable angle of light dispersion) make the numbers easier to recognize.
- Do this on a cold engine to avoid burn hazards.
Date code is on the vehicles right side between the heads and the transmission bellhousing.
Date Convention on 6.5 Blocks Cast by GM: MDDY
First digit denotes the month (A=January, B=Feb...)
Second and third digits denote the day (01=First day of the month, 02=Second...)
Fourth digit denotes the year (8=1998, 9=1999...)
C268 indicates March 26th, 1998
Date Convention and Location on Blocks Cast by Others:
Navistar Optimizer blocks use a different date convention but have the code in the same place as GM (excluding P400's).
Not sure what Dalton Foundries or others do. Refer to other sources.
Last edited:
