Too rich, need tuning advice

Discussion in 'Engine Topic' started by ChevyReb, Jan 15, 2021.

  1. ChevyReb

    ChevyReb Veteran Member Lifetime Gold Member

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    Well hey used to look like this before modding the carb and timing. And this was with like two warm ups and an 8 mile drive on brand new plugs.
    20210405_231747.jpg 20210405_231747.jpg 20210405_233819.jpg 20210405_231710.jpg
     
  2. ChevyReb

    ChevyReb Veteran Member Lifetime Gold Member

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    Well this is what they looked like before starting the carb mods. New plugs engine started and warmed up twice and a 8 mile trip around the block. Timing was 18 initial plus vacuum advance. Still burned your eyes running car in the shop.
    Screenshot_20210614-062446_Gallery.jpg Screenshot_20210614-062406_Gallery.jpg Screenshot_20210614-062345_Gallery.jpg

    But agreed they are way too white now.
     
  3. G72Zed

    G72Zed Veteran Member

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    Looked at the video's, everything looks very good actually. The large sweeps and "sampling" delay really makes me question that gauge. I use a Innovate MTX-L and it moves instantly with the throttle input, and does not vary more than .2 or .3 AFR at consent idle or cruise, but I use NTK sensors, not Bosch that came with the kits.

    If they are newer plugs, and the ignition is all up to par, with a properly dialed in carb, it will take long to colour them in, and a proper max lean at idle and cruise will keep the mid and upper porcelain portion kinda on the white side, then colour in grey for unleaded fuel, lots of racing on off throttle or with rich jetting over time, then the'll start to tan up.

    If you are not getting a lean surge at steady state cruise on the P-mains means your very close to optimum. Use that AFR gauge to make sure your WOT is in the 12.5-13.10 zone, some engine just want more WOT fuel, it depends. Do yourself a favor, once you feel and hear that the engine is happy on idle , transition and cruise AFR's use the gauge for WOT tuning, best at a track to jet for best MPH, then remove the gauge or cover it up, it's a carb with reversion and inversed intake/exhaust pulses, it plays havoc on that gauge, it ain't EFI.

    Lastly, you should give the BKR6EGP a close look, or even the BKR5EGP as well if a lot of street driving idling/cruising is a larger % of your driving.
     
  4. ChevyReb

    ChevyReb Veteran Member Lifetime Gold Member

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    I don't like the delay on this guage either G72Zed. I made the changes below and went for a test run today. Also have the Primary throttle blades for sure opening 100% now. The bobby pin is about 1/8" shy of the mark you asked me to make, so she is drinking about all shes got Mr. Scott. It seemed pretty responsive today and felt and sounded strong. One thing is I need to get a starter retard for the ignition so she will start back up after it makes a trip. It doesn't kick back, just does not want to turn the starter over at all, almost like the battery is dead.

    LMK what you think of the videos.

    Todays test drive videos.

    Changes
    Primary
    MJ = 71
    PVCR = .070 (up from .067)
    PV 6.5 (down from 8.5 as vacuum is lower)
    IFR .029 (up from .028) trying to remove idle surging

    Secondary
    MJ = 86 (up from 84)

    I think I will try going up to 72's on the primary to see if I can get cruise A/F a touch richer.



     
  5. G72Zed

    G72Zed Veteran Member

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    Taking away that large needle swing past 16+ AFR, your in the mid/upper 14's and low 15's for the cruise rpm your in, if you do not feel any lean surge you are OK with that 71 MJ.

    Most 2 corner 750 IFR are in the 29-32 sizes, some engines just need more idle fuel to be happy and not give you those "lean searches" that you are experiencing, again, do not "tune" to a number.

    Once your WOT is good, and your cruise/idle is set, put some black tape on that AFR gauge and drive the car for a few hundred miles or even a week, just "feel" how it's running.

    The engine tells you when it's happy if you listen closely and just "feel" it as you drive, I know, sounds weird, but I can be 50 feet from the dyno cell and can tell if the engine is happy and if it's going to be a good pull LOL.
     
  6. COPO

    COPO Veteran Member Lifetime Gold Member

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    Reb, that oil pressure gauge should not be moving around like that.

     
  7. ChevyReb

    ChevyReb Veteran Member Lifetime Gold Member

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    Hi Mark oil gauge has done that since new, it's a mechanical gauge so I figured that was normal, no? When I saw your video post my first thought was I need ne valve springs to fix that ? LOL
     
  8. ChevyReb

    ChevyReb Veteran Member Lifetime Gold Member

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    OK so yesterday I finally found my vacuum tester and started going through the lines and quickly found one that had a "Y" connecting two hoses to the front manifold port would not hold vacuum. I separated the two and was surprised to find the line going to the vacuum advance can was the bad one and the vacuum hose was not the problem. So I will search today for a replacement can and just get one of the ones that is adjustable by the allen screw in the hole. I would never have suspected that to have gone bad with 500 miles on it? If anyone has had good luck with a particular brand please LMK. It needs to fit the MSD Pro-Billit 8360 ready to run distributor. I am hoping this was the cause of the idle hunt surging that recently started, fingers crossed.

    Also badly need to get a starter saver OTW so it will restart after it is up to running temperature. Then I can drive it places and feel confident. I did drive about 35 miles yesterday as I knew I would be there for a couple of hours and cracked the hood in shade when I parked. 2-1/2 hours later it was still 130 degrees and 1st two turns were slow but then it got going. It is not kicking back on the starter, just won't go or is very slow when hot.

    I went up to the 72 jets and the difference was not that noticeable at cruse, still going close to 16 sometimes depending on load. I think its close enough now to just drive a while and then read the plugs after some miles. Also curious if the vacuum can could have had some effects on the A/F as well so no changes until that's fixed. I will try to test drive again with vacuum advance deleted.
     
  9. 1320feet

    1320feet Veteran Member

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    You can tame the gauge down by use a smaller inside diameter line.
     
  10. 1320feet

    1320feet Veteran Member

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    Maybe the starter is dragging internally as it is not kicking back.
     

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