Need help tuning Holley 600

Discussion in 'Troubleshooting & Diagnosis' started by cbraswell, Jun 29, 2017.

  1. cbraswell

    cbraswell Veteran Member

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    Oct 7, 2010
    Dudley, GA
    Sorry if this seems like the thousandth post about Holley tuning but this is my first Holley. I have a Holley 600 (80457-1) that I rebuilt back to stock settings and put on my car, I'm guessing from what I've read the accelerator pump is giving me problems. It idles in park at about 700-750 RPM (hard to be exact with the factory tach) with about 11-12" vacuum. I used a vacuum gauge to set IMS. I have searched and read all I could on adjusting the accelerator pump and it is still not clear if I am doing it right. I have a hesitation right off idle and then it's gone. If you blip the throttle it stumbles for a second and picks back up but if you ease the throttle it revs fine the best I can has been a few days since I messed with it. I haven't noticed any surging or bogging under any driving conditions except right off idle.

    I've read to adjust you need to get WOT and have .015 gap. I've also read that the diaphragm arm should move the instant the throttle lever is moved. Some stuff I've read said to adjust the nut until you get instant squirt when throttle is moved the slightest but want that change the .015 setting at WOT?

    MY understanding of this is to set it at wide open throttle, take a screw driver and push down on diaphragm arm to bottom it out and set at .015 with a slight drag on feeler gauge, which is what I've done. I have instant movement of the diaphragm arm when throttle lever is moved but NOT instant squirt out of nozzle.. I'm not sure exactly how far the throttle lever moves before gas squirts but it's a noticeable difference.

    So, did I adjust it correctly? Would the next step be playing with different pump cams and nozzles? It has a .031 nozzle and to me it looks like it comes out lazily lol..I was expecting a strong stream. The current cam is either pink or red, the color is faded so much it's hard to tell. It is in the first hole of lever and cam.

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