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Thread: 870 Avenger rich off-idle, but too lean at cruise shift points.

  1. #11

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    10-4. I had a previous issue with trying more than 1 thing at a time, patience is the key. I will post my results, hopefully by tomorrow. Thanks again.

  2. #12

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    OK, I tried many combos, one at a time though. I ended up with these specs and the engine really likes it, and the AFR reading reflect it. I should have stated in my 1st post that I had previously changed this carb to 4 corner idle, I am sorry for omitting this and I know/realize this fact will change many factors in tuning. Here are the specs I finished with:
    PRI
    Jets................. #75
    PV................... 10.0" HG
    PVCR................. .070"
    IFR.................. .0305"
    IAB.................. .070"
    MAB.................. .028"
    Emulsion bleeds
    Upper................ .024" (reduced from .028")
    Lower............... .028"
    Kill............... .028"
    Accel shooter........ .035"
    white pump cam

    SEC
    Jets.................. #82
    PV.................... 6.5" HG
    PVCR.................. .070"
    IFR................... .0305"
    IAB................... .073"
    MAB................... .028"
    Emulsion bleeds
    Upper................. .028"
    Lower................ .028"
    Kill................ .028"

    My AFR #s
    Idle in gear............ 13.5
    low rpm cruise........... 13.8
    cruise @ 55mph........... 15
    Cruise @ 65mph........... 14.6
    WOT...................... 12.7-13.0

    Once I had my AFR numbers in the ballpark using/changing the IAB/IFR, I went ahead and changed the upper E-bleed to a smaller orifice. This change enriched the area that has eluded me throughout my tuning of this carb. I realize this goes against recommendations, but it helped right where it was needed. Thank you so much for all your help and recommendations, greatly appreciated. Maybe this info or specs will help another person having issues with their 870. Thanks again!

  3. #13
    Join Date
    Nov 2014
    Location
    Ont. Canada
    Posts
    1,389

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    Good to hear it's getting better.
    I used to keep a spread sheet when I was tuning. That way, I could go back and put any tune back in it. I had a TPS on my carb that I could log. This is what I did.
    Attached Files Attached Files

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