1. Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

6.5 engine numbers

Discussion in 'GM 6.5 Diesel Engines' started by 1999gmc, Sep 13, 2010.

  1. 1999gmc

    1999gmc Active Member

    Sep 19, 2008
    Carmichael, CA
    I ended up getting two long block 6.5's with tin. Can anyone tell me what year and if they are oil spray blocks. I haven't taken them apart yet to see what went wrong with them, but was curious if the numbers are junk blocks anyway I probably won't mess with them.

    The first one has 12555506, F130, and then on the back of the block in the bell housing area it has F13 and then 506 below the F13.

    The other one is a 12555506, F148, and then F14 and 506 below the F14 in the bell housing area.

    Thanks for any info.
  2. buddy

    buddy Active Member

    Those are oil squirter blocks, all 506 blocks are and started in 1997. Not sure of the years, maybe 98 and 2000? I think someone knew how to interpret the numbers for years, maybe bk95td. Does one of them have the water pump with screw on fan clutch?
  3. 1999gmc

    1999gmc Active Member

    Sep 19, 2008
    Carmichael, CA
    Nothing on them but timing cover, oil pan, and valve covers. I was thinking 98 and 2000 also, but wasn't sure.
  4. WarWagon

    WarWagon Well it hits on 7 of 8...

    Nov 15, 2009
    The only way you can tell if they are junk is to tear them down and magnaflux them for cracks. You can also look for the tool clipping from the factory that creates a stress riser.

    Quoted from common knowledge sites of the Optimizer 6500 redesign problems fixed:

    There is another cracking situation that can occur in the cylinders, although less frequently. When piston cooling jets were introduced, the main bearing saddle in the block needed to be drilled to insert the continuous flow orifice-controlled piston oilers.

    Apparently the tooling would at times clip the bottom of the cylinder and, of course, would create a stress riser in the bottom of the bore. Occasionally, that would begin a vertical crack in the cylinder wall, most commonly in blocks that had a slight casting shift during their casting process. These were blocks that ended up with a thinner wall thickness, coincidently, right in that area where the tooling clipped the cylinder.
  5. bk95td

    bk95td 6.5 nut job/addict

    Nov 26, 2008
    The date code is on the bellhousing flange passenger side. Ithas a letter first[A jan,B feb,C march] Then day of month , Then year

    Attached Files:

  6. Missy Good Wench

    Missy Good Wench Wild Blonde from Cloud Mt

    Nov 19, 2008
    Newberg Oregon
    F is June and the last number is the year.
    8 being 98 and 0 being 2000

    As mentioned, the only way to tell if these are any good is to rip them all the way down and then steam clean the hell out of them.

    Blow dry and then start looking the crank webs over.

    The area in and around the outer bolts on the center mains is one place and then around the oil squirt holes on the center main webs.

    Cracks can start, as mentioned due to the stress riser in the lower cylinder from the tool "clipping" look carefully at the oil squirt holes for signs of cracks.

    If you assemble one of these engines, be sure that all the squirt holes have the little nozzles in them when you put it back together. Leaving just one out will cause a loss of oil pressure.

    Another area of concern on these blocks 96-2000 is the number 8 cylinder.

    Looking from the RH side of the engine and into the number 8 cylinder, check the area around the 8 oclock position about 1" down from the deck. (engine in the upright position)

    These have been known to crack radially around the cylinder.

    If this has occured it will be evident by a discoloration of the cylinder wall. Usually the crack can be seen easily.

    Check all the head bolt holes to be sure there are no cracks in the deck.

    If the decks show any signs of errosion around the fire rings, the decks need to be cut for the .010" thicker gasket.

    On any block that you do not know the history, check the deck to piston height before machining.
    On a stock engine the pistons should be right at flush with the deck at TDC.

    It can happen that an engine gets one deck machined in a rebuild and not marked. (Ask me how I know this)

    These are the common areas that need to be checked.

    Cracks in the outer bolt holes ( center mains) is repairable as long as the crack does not extend below the bolt hole and into the web. (Lock and stitch inserts)

    If the main webs have any cracks that are in the "register fit area" (where the caps fit into the block) the thing is a door stop.

    Other than these items, its just normal procedures.

    Last edited: Sep 14, 2010


    May 9, 2008
    Also a 2000 block could be an international casting as they took over the casting process in 2000 from GM since GM was retooling for the DURAMAX. The early international castings didn't have the diamonds either, but did have some of the improvements inside of them. I remember Canadian rigger years back posting pics of a 2000 casting that had some of the international upgrades in it.
  8. 1999gmc

    1999gmc Active Member

    Sep 19, 2008
    Carmichael, CA
    Good to know. I will problably start to pull them apart this winter.
  9. Brooklyn Tow

    Brooklyn Tow 9 11 Never Forget

    May 6, 2008
    Brooklyn, NY USA
    So is a 141 block desireable?....Where does it come in on the "6.5 Cracked/Cracking Block list"?

    "1" being good and the numbers decreasing with quality....
  10. buddy

    buddy Active Member

    Jamie at DieselDepot said he preferred to work with a 599 or 929 because they had superior casting metal content than the 141. I dont know what the differences were in castings, or even if the smaller outer main bolts helped on the 141.
  11. tanman_2006

    tanman_2006 Just a farm kid...

    Feb 15, 2010
    Seiling, Oklahoma
    Do 6.2's read the same way? is there a letter+3 letters for cast date?

Share This Page