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Thread: 4165 Idle Question

  1. #1

    Default 4165 Idle Question

    Hello all and thank you in advance for any help! First off let me say I don't know a lot about carbs so if you tell me something I will probably have to research what you tell me as this is the first time I've worked with a carb besides on small engines. I don't mind doing that but I just want you to know the type of person you're helping. For instance it took me about 30 minutes to figure out which Holley I had and how to adjust the floats (which I haven't yet) Just want you to know where I'm coming from.

    I just bought a 1968 396 350HP with a Holley 4165 6210-3. The car has full disk brake conversion and M22 transmission. The previous owner rarely ran it (likely very old fuel if that matters). I towed it home and have only driven it on short trips (2 to 5 miles)

    Day 1. I test drove it about 2 miles with no issues.

    Day 2: When I got it home it was fine for about 2 miles then it started idling rough like it was going to stall at the light. When I was driving it fast it was fine. I got home and took the air filter off and notice it was shooting fuel out the front vent tube while idling. Did some research and it said the float needed to be adjusted. I waited before I was going to attempt this.

    Day 3: Started it up and no fuel coming from the vent tube. Was fine at first. After about 1.5 miles the RPM climbed from 1100 at idle to about 2500. When driving at about 40mph it would maintain speed without pushing down on acceleration pedal. I drove it to gas station and added about 15 gallons of 89 fuel. Still ran at high RPM.

    Drove it home from gas station and let it sit while I did some research. I was thinking that I needed to adjust the low idle but research said I shouldn't have to mess with this. I let the car sit for about 3 hours. It cooled down. Started it up and it was idling at about 1100 RPM. It ran for about 10 minutes in the garage total time. At about 3 minutes in I revved it up with no issues. About 5 minutes in I revved it up again but this time the RPM stayed at about 1500. I let it sit like this for about 3 minutes then shut if off.

    So if I had to make some general observations:
    Runs fine when cold. The warmer and harder I drive it the higher the RPM and possibly the fuel float gets stuck? Was considering putting Sea Foam down the gas tank in case carb was "gummed" up or checking the float chamber and cleaning it up. Throttle was not getting stuck. Thank you for any help.

  2. #2
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,533

    Default

    Hello Phillipa. Your carb is a 650 spread-bore double pumper list number 6210-3, -3 is the 3rd revision.
    More than likely one cause of the erratic idle, the carb needs a rebuild, including throttle shaft rebushing as necessary.
    Your flooding condition is either a creeping needle and seat, fuel logging float, and/or float level a bit high.
    Factory float level is internal adjustment.
    You could replace your bowls with external needle and seat "dual feed" bowls.
    If it idles OK cold without any choke, then that's why it racing when hot.
    You could adjust the hot idle slower with the primary side speed screw first.
    Regards, Gary

  3. #3

    Default

    Hello Gaz. Thank you for the quick reply. Is it possible to buy the float without buying the whole fuel bowl. I found this rebuild kit: https://www.holley.com/products/fuel...t/parts/37-605. Will this work? Thank you.

  4. #4
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,533

    Default

    Yes, that kit will work, as a basic rebuild kit.

    If you have brass floats, shake them to check for fuel.
    Nitrophyl, check weight on digital kitchen scale, just wiped down after removal, then next day after they have dried, should be same weight. Gary
    Last edited by Gaz64; 05-31-2019 at 07:31 PM.
    Regards, Gary

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