383 SBC runs way too rich?

Discussion in 'Engine: Repairs , Modifications ,trouble shooting ' started by Grumpy, Jul 5, 2018.

  1. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    Grumpy, ?
    Have a Quickfuel 670cfm carb on my 383. It's extremely rich at idle. Also, has a hesitation when aggressively giving it gas in neutral. Car is not drive able yet. Initial timing is at 10 degrees initial. Vacuum advance (full manifold) is adding about another 12 for a total idle advance of 22. Using a stop to limit advance, but more can be added, if needed. Total timing is around 32 degrees.

    Engine starts fine, but runs rough. Idle mixture screws 1 1/4 turns from fully seated. Float level is half-way up sight glass.

    Vacuum gauge is 99% steady and registering 13"Hg, but this is kinda low for cam (211/219). Should be in the 16-17"Hg range.

    There is no spitting/backfiring, but I did see a fine "mist" of fuel come out of carb last time I turned the engine off. Also, engine almost acts like it wants to diesel for a spit second upon shut down

    What should I do?

    I'm thinking of turning idle mixture screws in to only 1/2 turn from seated and lowering float level, but everywhere I read says mixture screws should be 1 to 1 1/2 turn off seat.

    its almost always a good idea to post the city and state you live in, and don,t be afraid to ask questions or post pictures, as there,s at least some chance someone reading about your problem, or question, that has skills and a desire to help might read these posts that lives near you!:thumbsup:
    you might luck out and find a helpful mentor within easy driving range willing to help you out or at least get tips on local knowledgeable shops that work on similar cars are reasonable hourly rates, and what dealerships , repair shops, or machine shops in your area, to AVOID LIKE THE PLAGUE:thumbsup:
    start with the basics, verify your float settings are correct and you have no more than about 5 psi at the carb inlet port,
    fuel level should just barely show on the lower edge of the sight plug window, verify your ignition timing curve and use a vacuum gauge to set idle too the highest vacuum , yeah, you can ignore the basics but the result is always problems


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    READ THE THREADS and sub linked related info CAREFULLY
    http://garage.grumpysperformance.co...u-need-to-know-setting-float-levels-etc.1115/

    http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/

    http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/

    http://garage.grumpysperformance.com/index.php?threads/verifying-your-real-advance-curve.4683/

    http://garage.grumpysperformance.com/index.php?threads/no-computer-now-what.13973/#post-71209

    http://garage.grumpysperformance.com/index.php?threads/vacuum-gauge-help.9453/
     
    Last edited: Jul 17, 2018 at 10:55 PM

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