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Thread: Duramax Head Gasket Replacement

  1. #21
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    Quote Originally Posted by More Power View Post
    ....I'm sure it's punishment for something...
    If that's the worse karma thrown at you, I'd not complain too much.
    1985 Blazer 6.2
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  2. #22
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    As a "by the way", I couldn't resist watching one really short Youtube that was entitled "Remove the Duramax Damper Bolt in 2 Seconds".

    He used a 36mm socket and a ~24" 1/2" breaker bar, with the bar wedged behind the alternator pulley, held in place using bungie straps. Then, he got into the driver's seat and bumped the ignition key. The engine loosened the bolt.

    This seems more like a "here hold my beer and watch this moment", especially with a naked rear surface of the radiator in the video only inches away. I'd be wary of the engine starting with just a bump of the key.... then the loose tools would wreck the radiator, throw the wrench into a fender, then the windshield, then across the parking lot into your wife's car...

  3. #23
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    That's how I get 'em loose, sort of. Radiator protected with plywood, 1" breaker bar, strapped down, extended to a wood block on the ground, and driver fuse pulled (no fuel). I broke a 1/2" breaker the first time, so up to the 1". Just a bump of the starter is all it takes. You could "jump" the starter solenoid, just the same, but it's easier to pull the fuse and bump the key. At the same time, if an LB7 started at the bump of the key, it's be the first time I've ever heard (they all take at least 2-4 seconds of cranking, in my experience). I made a tool for tightening, that fits into the holes in the balancer, and braces against the socket on the bolt. The alternative is removing the starter and locking the ring gear with a special tool (that I don't have, but probably should). Ask me how I get the front brake bracket bolts loose, unless the above method makes you queasy.
    1985 Blazer 6.2
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    dmaxmaverick@thedieselpage.com

  4. #24
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    I bought these flex-plate/flywheel locks some time ago. One of these was designed for the Allison (not sure which one right now, the other for the ZF equipped trucks), which is inserted into where a thin steel inspection plate near the driver's side lower section of the Allison bell-housing can be pulled back to expose the teeth on the flex-plate. I suppose it's used to allow removing the transmission (by first removing the 6 torque converter bolts - through the starter opening) as well as help with removing the damper bolt. They were priced pretty cheaply. Just gotta make real sure it's removed before trying to start the engine... ... Maybe tape a big note to the steering wheel...

    Last edited by More Power; 08-24-2021 at 09:12.

  5. #25
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    That's good to know. The last Kent-Moore tool I saw for that bolted in place of the starter, and the manual called for removing the starter. Is that an updated Kent-Moore tool, or an aftermarket better idea? Where did you source it, if you don't mind me asking?
    1985 Blazer 6.2
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  6. #26
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    Thanks Jim....I will check out the Video.

    Keeping all the crud out of the engines innards is a challenge to say the least.....

    Rags and such can help.....but SANDING grit is nearly impossible to keep out of the cylinders and other openings.

    The stunts that some so called mechanics pull makes me cringe.....
    (1) 1995 Suburban 2500 4x4
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  7. #27
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    Quote Originally Posted by DmaxMaverick View Post
    That's good to know. The last Kent-Moore tool I saw for that bolted in place of the starter, and the manual called for removing the starter. Is that an updated Kent-Moore tool, or an aftermarket better idea? Where did you source it, if you don't mind me asking?


    Kennedy may sell that part. If not,

    Go here: https://duckduckgo.com/?q=duramax+fl...265-6__&ia=web

    By the way, that is a 3/4" drive 36mm 12-point impact socket for the damper bolt. I've seen the locks sold separately for less. The above link should help.

  8. #28
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    After reading the TSB about how to prepare the head/block deck surfaces, I pondered what I would use for a sanding block...

    "For surfaces that have corrosion or pitting, wrap a piece of flat steel (4"x 2" or larger) with 600 grit wet grade sand paper."
    I didn't have anything that would qualify as precision flat, so I contacted my fabrication guy. Here's what he was able to produce on his milling machine for me - a flat 1/2" x 3" x 4" steel block.



    This was made from 1/2" chromium steel plate of the type used for silhouette targets.

    I watched a YT video recently that showed what another guy used... a 6" long piece of angle-iron. That could work if he spent some time with sandpaper and a flat surface to sand it smooth and flat. He may have...

  9. #29
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    While I wouldn't call that a smoking gun, it's an indication of something. What's the head and deck look like at that location?
    1985 Blazer 6.2
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  10. #30
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    The leak required to pressurize the cooling system is minimal...
    The area on that fire ring is mighty close to the coolant passage.....

    The condition of that fire ring is pretty sketchy.....

    Sure looks like a good possibility to me...

    Getting the heads and decks cleaned up well with the "Sanding block" should give you a good idea of what you are dealing with.....

    I would do a good wipe down of the cylinders and look for anything hinky ....as in strange stains or discoloration ......

    Just to be sure and cover the bases...
    (1) 1995 Suburban 2500 4x4
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  11. #31
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    Is the firing ring impression consistent all the way around, and consistent with other cylinders? If they are all typical, and the manual and other technical sources don't hint at milling, would they all consider that condition normal, and not need a correction? I'm wondering if it's a product of aluminum vs. steel under high loading/torque or perhaps 20 years of high, sustained pressure. Or, is it a condition involving erosion or corrosion? I suppose it could be calculated, considering the force PSI, effected area, and hardness of the aluminum, exactly how much of an impression it should have. Even if you had them milled, would torquing a new gasket result in the same? If milled, would you be repeating exactly what you're seeing now? I don't know of anyone who's immediately removed a freshly torqued aluminum head for a look. I know it sounds skeptical (I am, a little), but mostly just thinking out loud. This is essentially a new territory for me, and something I'll likely be visiting in the near future. I've done dozens of aluminum head jobs, but those were almost entirely smaller engines, V6's, I4's, and boxers in compact/mid cars. I did assist with an LS V8, but wasn't present for the whole job and don't recall anything remarkable. Fire ring impressions were somewhat, albeit much less pronounced, typical, and often were at least minimally, still present after machining. It never became an issue, after the fact.
    1985 Blazer 6.2
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  12. #32
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    Quote Originally Posted by DmaxMaverick View Post
    Is the firing ring impression consistent all the way around, and consistent with other cylinders? If they are all typical, and the manual and other technical sources don't hint at milling, would they all consider that condition normal, and not need a correction? I'm wondering if it's a product of aluminum vs. steel under high loading/torque or perhaps 20 years of high, sustained pressure. Or, is it a condition involving erosion or corrosion? I suppose it could be calculated, considering the force PSI, effected area, and hardness of the aluminum, exactly how much of an impression it should have. Even if you had them milled, would torquing a new gasket result in the same? If milled, would you be repeating exactly what you're seeing now? I don't know of anyone who's immediately removed a freshly torqued aluminum head for a look. I know it sounds skeptical (I am, a little), but mostly just thinking out loud. This is essentially a new territory for me, and something I'll likely be visiting in the near future. I've done dozens of aluminum head jobs, but those were almost entirely smaller engines, V6's, I4's, and boxers in compact/mid cars. I did assist with an LS V8, but wasn't present for the whole job and don't recall anything remarkable. Fire ring impressions were somewhat, albeit much less pronounced, typical, and often were at least minimally, still present after machining. It never became an issue, after the fact.
    The fire ring impression is not entirely uniform all the way around the pictured head deck - or for any particular cylinder for that matter, but the head decks for the center cyls appear to be more lightly affected while the most effect can be found on the outside of the end cyls... and, none of them are really that bad, but everything is subjective and my inexperience with this makes my judgement a little rocky.

    The guy I spoke with at the engine shop said it was due to "brinelling". But, he did say there was a time/mileage component to it, indicating that a 140K engine would likely need to have the heads milled while a 5-10K engine likely wouldn't.

    You can see in the above image on the upper and lower left corners of the head where the small "crimped" areas on the head gasket had imprinted (brinelled) the aluminum. This is likely why GM redesigned the head gasket to include external rivets (outside the mating surface areas) in place of the crimping. Aside from a redesign of the gasket, GM also reduced the torque of the head bolts... Maybe because of the brinelling....

    My guess is that a resurfaced head would brinell yet again, but would last another 20 years...

    According to Wiki...
    Brinelling is the permanent indentation of a hard surface. It is named after the Brinell scale of hardness, in which a small ball is pushed against a hard surface at a preset level of force, and the depth and diameter of the mark indicates the Brinell hardness of the surface. Brinelling is permanent plastic deformation of a surface, and usually occurs while two surfaces in contact are stationary (such as rolling elements and the raceway of a bearings) and the material yield strength has been exceeded. The brinelling is undesirable, as the parts often mate with other parts in very close proximity. The very small indentations can quickly lead to improper operation, such as chattering or excess vibration, which in turn can accelerate other forms of wear, such as spalling and ultimately, failure of the bearing.
    Last edited by More Power; 06-11-2021 at 15:25.

  13. #33
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    That's purdy. Doesn't look like he used 60 grit paper and a 2x4.
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  14. #34
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    Loooking great

  15. #35
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    Thats what my 6.0 heads looked like when I got them back from the machine shop. Forced me to do a much better job on the block side. Sort of makes you want to polish the decks. Would polishing compound work on cast iron?

    Bill
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  16. #36
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    Quote Originally Posted by convert2diesel View Post
    Thats what my 6.0 heads looked like when I got them back from the machine shop. Forced me to do a much better job on the block side. Sort of makes you want to polish the decks. Would polishing compound work on cast iron?

    Bill
    I know... I feel the same way. However, the service bulletin says not to attempt to block sand the surfaces on either the heads or block decks to produce all shiny new metal. "Staining", they say is perfectly OK to remain, just not old gasket remnants or corrosion (rust) above the deck surface. The flat steel block ensures that the high spots will be removed, and besides, 600 grit paper wouldn't allow you to remove all traces of everything anyway - on the cast iron - without the patience of the Saints. Gotta be careful on the heads though. A scraper, properly and carefully used, will get almost all of the old gasket material, carbon deposits, and most corrosion off. Where you'll spend the most time with the sanding block is on the rusty perimeter of the block decks. Can't take all the rust off, just take enough to produce a flat surface transition - run your finger across is. The rusty perimeter is outside the gasket edge anyway. Jim

  17. #37
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    Good to hear that things are coming together....

    When you going to build a fire in it ?????
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  18. #38
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    I've got most of the coolant and fuel hoses/pipes connected... The electrical is upcoming. Won't get to work on it much today, but I suppose Monday/Tuesday will be close to when it'll be ready.

  19. #39
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    SWEEEEEEEEEEEEEEEEEET.

    Will be great to have it all back together and purrrrrring away again.....
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