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Smoke on deceleration

Discussion in 'Turbo Cobras' started by s351, May 15, 2019.

  1. s351

    s351 Member Established Member

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    Hey guys, just recently noticed that after a pull, when I let off I looked back and noticed some smoke in the rear view mirror during the pull its clean just after letting off this happened. It wasn't a crazy amount but enough that it made me pay attention to it.

    I'm going to check for shaft play to see if there's an issue there. At Idle in almost sounds like the turbo has a chirp to it. But when I turn the car off it still sounds like its spinning freely as I can here the wheel spinning smoothly after the car is off.

    Just curious if there's anything else I should check or should I also compression test it?
     
  2. slo984now

    slo984now AKA 01yellerCobra Established Member

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    Is it a stock long block?
     
  3. s351

    s351 Member Established Member

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    Built motor, pistons, rods, cams.
     
  4. MG0h3

    MG0h3 Premium Member Premium Member Established Member Established Member

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    Def be thinking about oil being sucked past a seal with high vacuum...valve stem seals.

    The turbo never sees vacuum but maybe the seal is leaking a little and you can’t see it under WOT.


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  5. s351

    s351 Member Established Member

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    I'm thinking about doing a leak down just to be sure.

    Could over filling the oil cause the same symptoms?
     
  6. slo984now

    slo984now AKA 01yellerCobra Established Member

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    Overfilling would cause it all the time I'd think. Plus you'd need like 10 quarts to get to the point of overfilling. Do you know what rings and what gaps were used? I made the mistake of using gapless rings in my built engine. It would suck the oil past the valve seals on decel. I learned later on this was a common issue with the mod motors and gapless rings.
     
  7. s351

    s351 Member Established Member

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    I'm not sure on the ring gaps, but the rings were the total seal ap steel.
     
  8. slo984now

    slo984now AKA 01yellerCobra Established Member

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    I had the stainless steel in mine. If you're running the gapless top ring I'd lay odds that's your issue. One time on the dyno when it was decelerating it shot out a whole bunch of smoke. I think Malcolm had similar experiences when he ran the gapless rings. Next time around I'm going to stick with traditional style.
     
    Last edited: May 20, 2019
  9. s351

    s351 Member Established Member

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    Thanks for the info, I haven't heard about this and it's always good to learn something new. It just simply surprised me to see some smoke after a pull.
     
  10. geoffmt

    geoffmt Well-Known Member Established Member

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    Any resolve with this issue?


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  11. TheOneandOnlyLTstang36

    TheOneandOnlyLTstang36 Member Established Member

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    If it has ball bearing turbo and if it has restricters on the return hoses, if they are to small it will smoke


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    Shadow Grey 03 likes this.
  12. s351

    s351 Member Established Member

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    Hey sorry, I did a comp test and leak down, everything was good there the worst cylinder was 6% most were 2-4%. So I looked else where. What I think it ended up being was my catch can was too full, I left it open for 24hrs to completely drain it. Since I have done that, I've had no smoke after doing a pull.
     
  13. Papaw

    Papaw Well-Known Member Established Member

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    Wow. Best case scenario. Good for you!
     
  14. s351

    s351 Member Established Member

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    Ya I was pretty happy after I did the leak down test.
     

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