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Thread: Idling Rich After Cleaning

  1. #1

    Default Idling Rich After Cleaning

    Greetings. Here's a bit of a back story. I have had a Holley Street Avenger 670 on my 351C for a couple years. It was dialed right in. Well, this summer I had a bit of a fuel leak from one of the sight glasses, so I decided to take it apart, clean it, and replace all gaskets. Now this isn't the first time I've had it apart, as I changed the jets & power valves a couple years before. So I take it apart, blow all passages with air, replaced sight glass & gaskets. Reinstall it all and upon fire up, I have fuel spraying out of the front bowl. I replaced the float needle, and that solved that problem. Started up again and it idled pretty rough, figured I may have fouled the plugs and preceded to replace them.

    Upon start up again, I had black smoke billowing out of the exhaust. Adjusted the idle mixing screws, but even turned all the way in the engine stayed running. I played with them a bit and realized it was the drivers side that's giving me the issue. I have a dual-plane intake and one side the plugs look fine and the other side the plugs have a heavy carbon build up on them. Now with the drivers side idle screw turned all the way in the exhaust turns into a grey haze, back it out any and it turns black quickly.

    I have since then taken apart the carb and blown out passages, replaced gaskets, tried different jets and power valves to a total of having this thing apart 6 times with zero change in results. I'm stumped, not sure what else to check to stop this. Other than maybe replacing the idle screws, as they were out to put new seals on. Any tips or advice? Thanks in advance.

  2. #2


    It's just me, but have you checked the float levels? With everything cleaned out and presumably nothing let in the passages, have you turned the idle adjustment 4 screws to seat, then backed off 3 one half turns? Also, do you have an electric or mechanical fuel pump? Don't pay a lot of attention to me, I'm learning most of this by trial & error.

  3. #3
    Join Date
    Nov 2014
    Ont. Canada


    I would look at the idle air bleeds first.

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