Dialing in 670 Ultra Street Avenger

Discussion in 'High Performance Modifications' started by bucco47, Sep 11, 2018.

  1. bucco47

    bucco47 Veteran Member

    147
    7
    Oct 30, 2008
    Tampa, FL
    This is my first Holley, so looking for feedback please.
    Installed it on my 383 to replace the Eddy that I just couldn't dial in. Immediate improvement out of the box. It was extremely lean so I went up 4 sizes with primary jets (63 to 67). I don't have any larger jets right now so the original secondary jets are what it came with for now (73). I gave the secondary speed screw under the base a half turn since my cam is only producing 11-12 vacuum at idle. This all helped immensely. It seems to run fantastic... idling, cruising, and WOT. Could I have nailed it this quick or should my target AFR be a little leaner than this?
    Thank you
    (btw, I was in some traffic so I couldn't keep my foot in it any longer then I did)



    [​IMG]
     
    1980RS likes this.
  2. 1980RS

    1980RS Veteran Member

    2,128
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    Jun 17, 2006
    MN
    You might find that the 670 would have been perfect out of the box on a single plane intake. As I have found with my BB that had an Air Gap on it I put more jet in the all carbs than they were stock. You may find that a 1" open spacer helps out performance on your setup if you have the hood clearance. You might also try cross jetting the 670 also. The ultra series is supposed to be a pretty good carb.
     
  3. bucco47

    bucco47 Veteran Member

    147
    7
    Oct 30, 2008
    Tampa, FL
    Do you mean a spacer without the divider? I was told I needed to use a divided spacer/heat insulator with my dual plane intake. I couldn't find as taller divided insulator/spacer than the one I have.
     
  4. 1980RS

    1980RS Veteran Member

    2,128
    117
    Jun 17, 2006
    MN
    No just an open plenum spacer. After testing with some spacers on dual planes the 4 hole slowed down my car and 2 hole or divided one did nothing. I do know that if one has a pretty good cam with a lot of overlap a 4 hole spacer helps with driveability. 1" spacer can be made of wood, plactic or aluminum.
     
  5. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

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    Oct 2, 2013
    Milford,CT
    If a spacer is in your future, I'd suggest plastic or wood over aluminum...just for heat conducting purposes. Nice looking engine bay.
     
  6. bucco47

    bucco47 Veteran Member

    147
    7
    Oct 30, 2008
    Tampa, FL
  7. jthomas

    jthomas Veteran Member Lifetime Gold Member

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    Dec 5, 2007
    NorthCentral PA
    Nice setup!

    Your cruise is a bit rich and could be leaner. When you go WOT it moves to a little leaner than I like but it’s not too lean. I run mine 14.3-14.8 at idle, about 14-14.5 at cruise, 13.5 on light acceleration, 13 on moderate acceleration and 12.5 full WOT. My plugs have just a slight tan to them and my Quick Fuel is very responsive in all ranges at those numbers.

    I’d say your close, but you could dial in the cruise and light throttle to be less rich and WOT to be a little richer.
     
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  8. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

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    Oct 2, 2013
    Milford,CT
    Suggestion: If you are going to do a spacer, do it first, and then go back and tweek. The numbers may change, and you might end up doing it all over again. 12.5 is good for heavy throttle, (as they say a little rich will leave no power left on the table). High-13s-mid14 is pretty good for idle and cruise, light accel. about 13.5. (pretty close to jthomas above). Lower than 12, is too rich anywhere on the band.

    Looks like your speedo isn't hooked up. :p
     
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  9. bucco47

    bucco47 Veteran Member

    147
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    Oct 30, 2008
    Tampa, FL
    I made a few adjustments... smaller power valve [5.5] and more timing advance [20 btdc]... and I have the idle ratio at 12.5-13, cruise at 13-13.5, and WOT is about 14.5. I'm pretty happy with where it's at now.
    Thanks guys.
     
  10. bucco47

    bucco47 Veteran Member

    147
    7
    Oct 30, 2008
    Tampa, FL
    Thanks!
     

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