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  1. W

    Piston rings not seating

    I had two Durmax heads surfaced two months ago, they did not need a valve job. They took .004 off one head and .006 off the other to clean up the surfaces and make sure they were straight. Since it did not need a valve job this work was done without removing the valves. The valves did not...
  2. W

    Piston rings not seating

    Wow, tough group. I think it is established his rings are not sealing. Compression is low, blowby is excessive. On tear down I would want a neutral seat of eyes to see what his piston to wall clearance is. What are the ring gaps. What does the cylinder finish look like. Verify cross...
  3. W

    Piston rings not seating

    Chevy, you are correct .040 is too much Piston to Head clearance in a Duramax. I quoted a known number for automotive engines which have more RPM and with more RPM you have more rod stretch and need the extra clearance. The Duramax only spins maybe 5,000 RPM Max so a tighter quench or piston...
  4. W

    Piston rings not seating

    Since you installed the heads did you check deck height? If the pistons were down in the hole you lose a lot of compression. Would not cause blow by but might cause low compression. Most builders say you need .040 deck clearance between the piston and cylinder head but your head gasket...
  5. W

    Piston rings not seating

    A properly built engine will run like new even on the Walmart private brand 15-40W at $20 per gallon. In extreme racing or extreme towing the better. Oils might show an advantage but oil is not your issue.
  6. W

    Piston rings not seating

    Blow By is created when combustion blows past the piston rings. When the combustion happens both intake and exhaust valves are CLOSED so blowby is not part of valve stem seal failure. Leaking valve stem seals can certainly use a ton of oil. One drop of oil leaked per combustion will make an...
  7. W

    Piston rings not seating

    Valve seals are on the wrong side of your compression to cause this issue. Rule them out. Blow by is pressure in the block below the piston rings. Every time the piston fires you will have some pressure blow by the rings. In your case you have lots of pressure blowing by the rings. Remove...
  8. W

    Piston rings not seating

    Modern rings seal up quickly but the Diesel rings do need to be loaded to seat properly. Dyno operators tell me blow by is gone by the end of the first dyno pull normally but a Dyno pull puts 100% hard load on the engine and takes it from just above idle to max RPM at full throttle and full...
  9. W

    Piston rings not seating

    You are correct, if all 8 cylidiners are down from 360 compression to 275 something is assembled or prepared wrong. Dose the Duramax use a Keystone top ring or traditional top ring? I could look it up but a Keystone does not have a top and bottom so it cant be reversed while a traditional ring...
  10. W

    Cylinder wall honing surface finish & ring gap

    Old thread I know but information your should know if having a engine bored. Pistons for several years now are cut on CNC machines to finish size. The CNC machine (computer controlled machine) allows the piston to be custom cut so they take away material where they now know the piston grows...
    • West
    • Post #73
    • Forum: LBZ
  11. W

    Piston rings not seating

    Compression is the same in all 8 cylinders so no top ring is stuck in its grove. That video is pretty spooky. That is a ton of smoke from plugging that tube. I am guessing you plugged the PCV vent tube? Who did the bore and hone on the block? Rings will not seal on a bad bore and hone job...
  12. W

    05 LLY, remand long block, sitting 2 years, new injectors etc. Crank no start.

    Congratulations, A WIN.
    • West
    • Post #10
    • Forum: LLY
  13. W

    Injector stuck open LB7 (maybe)

    I have a Launch X431V+ that can read the injectors but this tool is $1300. Maybe there are others that cost less and can do the same. I had not heard of SAC injectors failing?
    • West
    • Post #2
    • Forum: LB7
  14. W

    Piston rings not seating

    The Top Piston Ring is exposed to the heat of combustion, this heat makes the ring grow so you need to have enough gap so the ring never butts even when working very hard towing heavy loads. If the top ring butts it becomes a scraper and will tear up your cylinder wall and maybe fracture a ring...
  15. W

    Piston rings not seating

    Man these problems can be really painful. You try hard to do it correctly and end up starting over. If your cylinders were honed correctly and ring gaps set properly after it was bored you should have a smooth surface for your rings to run on with a light cross hatch that helps hold oil and...
  16. W

    2004 LB7 Cylinder Head and Injector Repair

    Here you go, pics show #5 hold down boss, perfect and centered, also shows #7 and the problems. The pics are not in sequence sorry, The installed new time sert is the very last photo and it is now 1" deep and uses the factory threads so the factory Inj bolts fit and work. It is slightly off...
  17. W

    2004 LB7 Cylinder Head and Injector Repair

    While this was certainly my first Duramax it was not my first Diesel and I probably have 100 engine builds under my belt so although not the same as a Duramax, 35 years experience in the industry does help and I was certified in Engine Repair, Engine Performance and 5 areas of Engine Machine by...
  18. W

    2004 LB7 Cylinder Head and Injector Repair

    Just completed a 2004 LB7 repair for a friend. Had lots of advice/help from 2004LB7 on this forum. Thank You 2004LB7. A little background, this truck A friend has had this truck since new, new injectors were installed at 90K and up to say 130,000 miles the GMC Sierra 2500HD had been getting...
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