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Thread: 6.5 Diesel Block Identification (moved from navistar thread)

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  1. #1
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    Arrow 6.5 Diesel Block Identification (moved from navistar thread)

    I have a block with GM in the lifter valley and on the main caps, the 1255506 casting number on the bell flange, and 506 on the back of the block, but no Navistar diamond and no 506 in dots in the valley. For those who see a lot of chinese/AMG blocks, what do I most likely have?

    It's crack-free, looks beefier with the thicker taller main bearing caps etc., just want to be sure before I pour a lot of money into a buildup . . . .
    1982 GMC Sierra Grande Camper Special
    6.5TD: ARP head studs, DSG girdle kit, DB2 turned up 1/8th, '97 Cummins intercooler, custom 3" downpipe to 4" straight exhaust, wastegate @12psi, boost and pyrometer, NV4500 with mech. clutch, twin-sticked NP205, D60 front/D70HD DRW with 4.10 gears, '93 serpentine belt setup
    in progress

    1997 Chev Express G3500
    6.5TD 15 passenger van

  2. #2
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    Lubbock TX, USA
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    Quote Originally Posted by Busted View Post
    I have a block with GM in the lifter valley and on the main caps, the 1255506 casting number on the bell flange, and 506 on the back of the block, but no Navistar diamond and no 506 in dots in the valley. For those who see a lot of chinese/AMG blocks, what do I most likely have?

    Sounds like an early 506 block. Look for the date code on the opposite mounting flange as you found the casting number. Post that and we can tell you what it is, if there isn't one, post a picture and I can tell if it's foreign.

    J
    1982 C10 SCSWB 6.5TD, mods too extensive to list. (13.69 1/4 mile @94.6 MPH) RACE TRUCK
    1982 C10 SCSWB 6.2NA, 2.73 700
    1986 C10 SCLWB 6.2TD 3.73 700
    1989 V20 SUB 6.2NA, 3.73 400
    1994 G20 VAN 6.5NA, 3.42 60E
    1994 K20LD ECSWB 6.5TD, 3.42 80E
    1995 K20 SUB 6.5TD, Wrecked, ran into by stupid teen.
    1995 C3500HD DRW 6.5TD, 12' Flatbed 5.13 80E
    1995 C3500HD DRW 6.5TD, 18' Rollback Wrecker 4.63 80E
    1994 C20HD ECLWB 6.5TD 3.73 80E Wifes Truck.
    1995 C20LD ECSWB 6.5TD 3.73 80E
    1995 K20LD SCLWB 6.5TD 3.73 80E
    1996 K30 DRW 6.5TD 4.10 80E
    1997 C10 Tahoe 2Door 2WD 5.7L to 6.5 Conversion Underway

  3. #3
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    The date code is C221

    I also can't find oil spray nozzles, but then I'm not completely sure what I'm looking for . . .
    1982 GMC Sierra Grande Camper Special
    6.5TD: ARP head studs, DSG girdle kit, DB2 turned up 1/8th, '97 Cummins intercooler, custom 3" downpipe to 4" straight exhaust, wastegate @12psi, boost and pyrometer, NV4500 with mech. clutch, twin-sticked NP205, D60 front/D70HD DRW with 4.10 gears, '93 serpentine belt setup
    in progress

    1997 Chev Express G3500
    6.5TD 15 passenger van

  4. #4
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    The early 506 blocks had large outer bolts (center mains) and no spray nozzles.

    The spray nozzles are located in the main saddle of the block on both sides of center.

    The center hole in the main saddle is the oil feed hole. The ones a little offset are the squirt holes.

    The squirt holes have a little aluminum nozzle pressed into them and they aim up into the cylinder to help cool the piston crown.

    The nozzles recieve oil all the time the engine is running.
    The oil feed from the pump comes from the oil gallery to the mains via the cam and then feeds the goove in the upper main bearing. The groove has pressure oil all the time as does the squirt nozzles.

    The 97 production 6.5's had the large outer bolts and the nozzles. These were one of the most failure prone blocks built.

    In subsequent years the outer bolts were reduced to 10MM down from 12MM and the size of the oil squirt holes was reduced also.

    The oil pump used on the squirt motors was of a larger displacement to handle the huge loss of oil volume from the squirts.

    These pumps have a 1/2" (Approx) spacer in the middle of the pump between the pump body and the cover. The gears are longer too.

    The squirt block pump can be used on a non squirt block but not the other way around.

    Using the lower volume pump on a squirt block will cause a very low oil pressure condition at low speeds.

    Cracks can't generally be seen well until the block is bare and clean.

    Some cracks will start at the register fit where the caps sit in the block. Most though start on the inside of the outer bolts holes (center mains only) and progress outward and then down the web along the length of the hole.

    Many of the cracks can't be seen easily even after the block is cleaned up.

    The trick to finding these little animals is to heat the web around the outer holes with a propane torch.

    You dont have to fry the thing but just get the web Hot to the touch in that area. Let sit a bit and any cracks will see any oily band show up as the oil cooks out.
    As long as any cracks dont go beyond the depth of the hole, they can be repaired with the Lock and Stitch full torque inserts.

    A crack that starts in the area of the register corner and progresses down the web pretty much dooms the block to becoming a door stop.

    Also have a look see at the cylinder deck area especially in the area of cyl's 1 and 2

    errosion around the fire ring contact area is common. If its not too bad it can be fixed handily by machining the deck .010" and using a OS Felpro gasket.

    Before you rip the sucker all apart. Make sure how far above the deck the pistons come (both sides) stock is flush to.002" above.

    If you find that the pistons are above the deck more than this Oh say .010 or ??? the block has been decked prior to you owning it.

    Now Felpro makes a .010 thicker gasket. Cometic will make a thicker one if you need it.

    If you find that you need to take .020 or so off the block, Cometic will custom make gaskets for you.

    Ask me how I know this.

    Always replace the cam bearings on these engines any time there is machine work done.
    The cam bores have a groove behind them and there is a nice Hidding place for sahvings to get stuck. Then when you run the thing there is an issue. Game over.

    Remove cam bearings, machine block, hot tank or wash, resinstall bearings.

    Make sure the cam bearings are installed just like the originals with the oil delivery holes oriented the same.

    The front bearing has a notch, it goes to the front.

    Hope this stuff is useful

    Have fun
    Missy
    Last edited by Robyn; 07-15-2009 at 08:50. Reason: addition
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2005 Suburban (Papa Smurf)
    THIS IS BOW TIE COUNTRY

  5. #5
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    Lubbock TX, USA
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    You've got a 2001 block, just prior to the Navistar casting, in appearance.

    It's has the later caps on it, with the slants from the top bolts down to the lower outer main bolts.

    It's a GM block.

    Proceed with tear down.
    1982 C10 SCSWB 6.5TD, mods too extensive to list. (13.69 1/4 mile @94.6 MPH) RACE TRUCK
    1982 C10 SCSWB 6.2NA, 2.73 700
    1986 C10 SCLWB 6.2TD 3.73 700
    1989 V20 SUB 6.2NA, 3.73 400
    1994 G20 VAN 6.5NA, 3.42 60E
    1994 K20LD ECSWB 6.5TD, 3.42 80E
    1995 K20 SUB 6.5TD, Wrecked, ran into by stupid teen.
    1995 C3500HD DRW 6.5TD, 12' Flatbed 5.13 80E
    1995 C3500HD DRW 6.5TD, 18' Rollback Wrecker 4.63 80E
    1994 C20HD ECLWB 6.5TD 3.73 80E Wifes Truck.
    1995 C20LD ECSWB 6.5TD 3.73 80E
    1995 K20LD SCLWB 6.5TD 3.73 80E
    1996 K30 DRW 6.5TD 4.10 80E
    1997 C10 Tahoe 2Door 2WD 5.7L to 6.5 Conversion Underway

  6. #6
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    Sep 2007
    Location
    Stony Plain, AB
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    Cool, thanks for the input!! When I looked in the valley and saw no Navistar diamond I was worried that I got a foreign block . . .
    1982 GMC Sierra Grande Camper Special
    6.5TD: ARP head studs, DSG girdle kit, DB2 turned up 1/8th, '97 Cummins intercooler, custom 3" downpipe to 4" straight exhaust, wastegate @12psi, boost and pyrometer, NV4500 with mech. clutch, twin-sticked NP205, D60 front/D70HD DRW with 4.10 gears, '93 serpentine belt setup
    in progress

    1997 Chev Express G3500
    6.5TD 15 passenger van

  7. #7
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    Location
    Montana
    Posts
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    Arrow

    The date code is C221
    This is likely one of the last GM produced blocks. AM General's first re-designed (with Navistar's help) blocks appeared sometime in November of 2001, and had the new date code numbering system.

    I'd be curious what cylinder heads this block had on it - i.e. whether small or large port pre-cups.

    Jim

  8. #8
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    Stony Plain, AB
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    The heads have the small port pre-cups, with one square stamped into them.
    1982 GMC Sierra Grande Camper Special
    6.5TD: ARP head studs, DSG girdle kit, DB2 turned up 1/8th, '97 Cummins intercooler, custom 3" downpipe to 4" straight exhaust, wastegate @12psi, boost and pyrometer, NV4500 with mech. clutch, twin-sticked NP205, D60 front/D70HD DRW with 4.10 gears, '93 serpentine belt setup
    in progress

    1997 Chev Express G3500
    6.5TD 15 passenger van

  9. #9
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    Newberg Oregon
    Posts
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    Thats interesting. The later engines usually have the diamond stamped cups which has a large (largest) port.

    Unless the engine was an N/A model.

    Robyn
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2005 Suburban (Papa Smurf)
    THIS IS BOW TIE COUNTRY

  10. #10

    Default after a year for block

    can you tell me what year this block is
    Attached Images Attached Images

  11. #11
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    Can you post a better piccy with good contrast of that date code (Right side rear on the bell housing flange)

    Run a wire brush over the area and clean it good first.

    The one piccy is just too washed out to really tell much.

    Is that 6.2 ?? I see in one piccy, the 700R4 TV cable bracket.


    Let us know

    Missy
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2005 Suburban (Papa Smurf)
    THIS IS BOW TIE COUNTRY

  12. #12

    Default

    thanks Robyn, its all the same motor, ex militry
    here are a few more photos of number and casting marks in the vally under injector pump looks like two triangles faceing away from each other then an MN
    if someone wants the cable they can have it just pay postage from oz, it is a kick down for the gearbox isnt it?
    pump type is db2831-5209
    the last letter looks to me to be a p but one of your other threads dosnt say anything about a p????????
    Attached Images Attached Images

  13. #13
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    The double triangles or Diamond <> is the Navistar casting logo

    This could be one of the last GM engines that was made before AMG took over fully.

    Does this engine have the one piece rear main seal ???

    The pictures are still just to fuzzy to see the Numbers in the Julian date

    The last engines that were done by GM were cast at the Navistar Foundary.

    The later ones that were all AMG had a juilian date that started with a Letter.

    H was 2001
    I was not used
    J was 2002
    K
    L
    M
    and so on

    The AMG Blocks are all date coded with a Letter followed by 00 00 numbers that represent the month and day.

    H 01 20 or some such

    The GM codes are different.

    Your engine is most likely a 6.5 and not a 6.2

    If it has a single piece rear main then its almost a sure bet that its a 6.5

    Navistar, as far as I know never cast a 6.2 block.

    Now some late 90 through 93 6.2 engines used the 599 casting numbered block and were built as 6.2 engines.

    These engines share the same crank as the 6.5 engine.

    The cable and bracket of this type were used on the 700R4 and are a TV cable, and controls the throttle pressure on the 700R tranny.

    Missy
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2005 Suburban (Papa Smurf)
    THIS IS BOW TIE COUNTRY

  14. #14
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    Cedar Grove, NC
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    Quote Originally Posted by ashbee37 View Post
    thanks Robyn, its all the same motor, ex militry
    here are a few more photos of number and casting marks in the vally under injector pump looks like two triangles faceing away from each other then an MN
    if someone wants the cable they can have it just pay postage from oz, it is a kick down for the gearbox isnt it?
    pump type is db2831-5209
    the last letter looks to me to be a p but one of your other threads dosnt say anything about a p????????
    That is a GEP block, but I don't think it's a tv cable for a 700r4. This engine came out of a N/A Hummvee and I don't think they are rockin' the 700.

    The letter might be an R (2008). They didn't use some letters that might be mistaken for another letter.

    I have an engine just like yours and just finished rebuilding it this weekend. Ask me anything.
    84 C10 J code intake.

    83 C10 Scottsdale w/veggie conversion.

    98 K3500 Silverado CC DRW, marine injectors, 4" exhaust (kitty cat MIA), boost and egt gauges, FSD relocated, #9 resistor thingy, reman Navistar block from Kennedy installed Jan 08, Reese Signature Series Gooseneck hitch.

    95 C2500 F code. Rebuilt GEP. Daily driver since Jan 2014.

  15. #15
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    Your right, the military never used the 700R4, they used the TH400 in most of the applications.

    That bracket is a dead ringer for the 700R4 TV cable connection.

    I just had one in my hand a couple hours ago.

    It may be for another purpose, I have no clue as to what though.

    I have had my hands on several Ex MIL 6.2/6.5 engines and they all had mechanical injection pumps and TH 400 trannies that used the vacuum valve on the IP to run the modulator.

    That bracket is very freshly painted as compared to the stuff around it, making me wonder, if maybe the engine has been used in another application since being G I issue


    Missy
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2005 Suburban (Papa Smurf)
    THIS IS BOW TIE COUNTRY

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