New Holley wont idle down

Discussion in 'Engine Topic' started by arick793, Sep 21, 2017.

  1. arick793

    arick793 Veteran Member

    Oct 27, 2008
    Rochester, NY
    just put a brand new Holley 670 ultra street avenger on my car. Electric choke. It's on a square bore GMPP Vortec dual plane intake. My problem is that I can't get the car to idle less than 1,200 RPM's. The idle speed screw is backed out all the way, I looked down the carb and could see that the throttle plates were completely closed. I put a brand new gasket underneath it. I sprayed carb cleaner around the base of the carb, and the idle goes up just a little when I spray between the carb and the intake on the drivers side. That doesn't seem like a big enough leak to idle the engine with the throttle completely closed though. I have the pcv and power brake ports capped off, the timed vac port is capped off. The only vacuum line hooked up is for the vacuum advance. The car was running great this morning with the 600 edelbrock. Thanks for any help
  2. arick793

    arick793 Veteran Member

    Oct 27, 2008
    Rochester, NY
    I used a single hole gasket like this:

    Should I have used a 4 hole gasket like this?

  3. arick793

    arick793 Veteran Member

    Oct 27, 2008
    Rochester, NY
    Now that I'm looking into it, I really like this gasket. It's very thick, 0.320", supposed to help keep some heat off of the carb, but should also seal up nicely I think.

  4. harbone66

    harbone66 Veteran Member Lifetime Gold Member

    Feb 15, 2011
    Central Illinois
    Any kind of vacuum leak is bad no matter how small. Put a new gasket in it and start over
  5. Damon

    Damon Veteran Member

    Nov 16, 2000
    Philly area
    Is the fast idle cam (high idle speed arm) on the pass. side of the carb making contact with the body of the intake, hanging it up? If you say the primaries are COMPLETELY closed, probably not, but it never hurts to check. This is one where it will look perfect with the carb off the motor but won't idle down when installed ON the motor. Remember that Edlebrock makes all the GMPP intakes and, I swear, they design them INTENTIONALLY to give you little problems if you try to put a Holley (competitor's) carb on top.

    I'd also put the carb on with NO gasket and check to see if the mating surfaces are flush. Do the corner-to-corner "rock test". It should be laying on there dead flat.
  6. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

    Nov 4, 2004
    Ringgold, GA
    I've ran into the situation Damon described, I took a large flat file and squared the base. This was on a used carb so likely some tightened it down on a warped intake - so lay a flat edge across the intake also. If it's the new carb, send it back. Holley's QC is a bit on the terrible side now. Another thing to check is how the secondaries are set. There's a small screw accessible under the base plate that sets opening of these.
  7. arick793

    arick793 Veteran Member

    Oct 27, 2008
    Rochester, NY
    I'm working on fixing the gasket leak. I did install the carb with a new gasket, so one of the mating surfaces is likely bad. It was initially hanging up on the fast idle cam, but I got that straightened out. I crawled into the engine bay and looked down the carb with a flashlight to make sure the butterflies were totally closed. I'm going to pull the carb back off, and make sure all of the bolts and screws are tight too.
  8. COPO

    COPO Veteran Member Lifetime Gold Member

    Sep 15, 1999
    Ontario, Canada
    If your using a vacuum advance can then it could be
    giving you too many degrees of timing. What’s your initial at and total?
  9. 1980RS

    1980RS Veteran Member

    Jun 17, 2006
    Check the choke, make sure the screw for the fast idle cam is not on the cam holding the throttle open, had that before.
  10. 77 cruiser

    77 cruiser Veteran Member

    Nov 17, 2006
    Frostbite Falls MN
    How bout the secondaries?

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