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How to stop blowing Blue Smoke???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by foxman, Jun 23, 2003.

  1. foxman

    foxman 1/2 ton status

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    Ok I've got a 90 k5 W/190,000 on it. I don't know if the motor was ever rebuilt, but it seems like it hasn't. I replaced the oil seals in the valves, but still she smokes like a bandit. When ever downshifting on the expressway, I leave a "James Bond" style blue smoke cloud. My guess is that the rings are just letting too much by. is there any proven way to help get rid of this oil burning problem?, or is a rebuild the way to go? I'm taking in a quart of oil every one to two weeks over here. /forums/images/graemlins/crazy.gif

    Thanks.

    Jeremy
     
  2. Waxer

    Waxer 1/2 ton status Author

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    The problem is your rings. Anything other than a rebuild is just bandaiding the problem.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Rebuild is the way to go IMO.

    Since she still runs, getting a core engine and building it up the way you want is a good way to go. /forums/images/graemlins/smile.gif Gives you time to make enough money topay for all the stuff you want to do to it, if you want to build a motor different than stock. When you get done with it, you just pull yours and drop the other in.
     
  4. BlazinRojo

    BlazinRojo 1/2 ton status

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    rebuild rebuild rebuild
     
  5. DOCKAWI650

    DOCKAWI650 Registered Member

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    rebuild is the way to go
     
  6. blasterD

    blasterD 1/2 ton status

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    It sounds like you need a rebuild pretty bad.
     
  7. the professor

    the professor 1/2 ton status

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    190,000.. Not all that much if its been reasonably cared for...
    --
    Everybody missed one very important thing that while not exclusive to Chevy, is very common on hi-milage V engines..
    --
    There is a realy good chance that the intake gaskets are leaking...

    After alot of miles, they get very hard... the manifold bridges a "V" that is constantly expanding and contracting...and then they start to leak at the bottom, and suck oil like mad...

    Always use the factory "soft" gaskets, or the Felpro (I think the number is 1212), they are thicker and softer and have the orange silicone strips around the ports...

    You didn't say if it was automatic, but a bad vacume modulator on a TH350/400 will suck auto trans fluid into the motor and THAT REALLY SMOKES...

    Pull the line off the modulator and see if there is any oil in it ..it should be dry... /forums/images/graemlins/cool.gif /forums/images/graemlins/truck.gif
     
  8. bigblock44k5

    bigblock44k5 1/2 ton status

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    I agree with the professor. Id also like to ad:
    It smokes when first starting-Exhaust seals.
    It smokes on deceleration-Intake valve seals.
    It smokes most of this time-rings.

    Easiest way to check is with a compression tester or blow by guage. Test the compression and record your numbers. Then squirt a little oil in the sprak plug hole and recheck. If the numbers go up dramaticaly, the rings or cylinders are worn. If not, it's most likely valve seals, intake gaskets, or vacuum line to the modulator. /forums/images/graemlins/deal.gif
     
  9. TXsizeK5

    TXsizeK5 1/2 ton status

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    My old 305 would smoke on start up, i heard its the valve seals. But then i showed a mechanic friend of mine and he said since theres so much smoke its probably the rings.
    You can use "engine restore" with your oil changes, might help a little or "smoke b gone" all from autozone, but prbably wont help too much if you're smoking alot.
     
  10. foxman

    foxman 1/2 ton status

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    Yeah, I already replaced the intake gaskets, They started leaking on the top side last summer. what is a normal compression reading for 1he 90 350 TBI? I get 12-13 on the compression guage... I think that that is like 125 ft/Lbs or something...


    Thanks

    Jeremy
     
  11. Waxer

    Waxer 1/2 ton status Author

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    The number for a stock 350 should be around 150psi. If you're only getting 12 or 13 on one cylinder, then you've got some serious issues with that engine.
     
  12. BigBurban350

    BigBurban350 1/2 ton status

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    Blue smoke all the time means bad rings. Do a compression test, record numbers. Then squirt heavy oil into the back of the cylinders and let the oil seep around the rings, then repeat the test, if there is a 10% or more increase in pressure then the oil is sealing the rings and the rings are bad.

    Your oil control rings could be stuck in also pressed in by a tapered cylinder.

    BUT!!!

    What you just said it smokes on downshifts which indicates valves are leaking. When you downshift and the throttle plates are closed it creates a large vacuum on the intake side and sucks oil past the intake valve seals as its trying to get air. So your seals could be incorrectly installed, worn out, or there is excessive clearance in your valve guides.
     
  13. foxman

    foxman 1/2 ton status

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    Not 12-13 psi, 12 and 13 are coresponding numbers on my guage. I think they represent 120 psi and 130 psi.

    Buy you say @ 150 is stock eh?

    I'll check again.

    Thanks,

    Jeremy
     

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