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Thread: Emissions

  1. #1
    Join Date
    Jan 2002
    Location
    Woodham, Surrey, UK.
    Posts
    513

    Emissions

    I'd left my RV8 + Edelbrock for some weeks, and it really didn't want to start, apart from when I chucked some petrol down the inlet.

    Looked around the interweb, then changed the fuel filter and followed the Edelbrock video on removing the idle mixture screws and blowing air in. It starts fine now, so cause properly diagnosed. I put the screws back exactly where they were, but conditions are of course different now, so almost certainly it will fail the emissions at MOT (again). Is there a cheap way of sorting this, or will I need to ask nicely at the garage again when it fails? They are very sympathetic, and know nothing of Edelbrocks, so I've done the fix twice myself now, but it would be good to go in and pass without fiddling around.

    Bernie

  2. #2
    Join Date
    Feb 2003
    Location
    Horsham, West Sussex, UK.
    Age
    59
    Posts
    190
    Hi Bernie

    The only way to be certain is to put a lambda sensor up the tail pipe and measure the air fuel ratio at idle.

    But as a way to get close you could get yourself a vacuum gauge and connect it up to the permanent vacuum port on the carb. That's the lowest of the 2 ports on the front of the carb. If I remember correctly it's one to the right (passenger side) of the large PCV port. Start up the engine then set the idle screws to give you maximum vacuum at idle. This should be where you get maximum idle speed, or close to. Now turn the idle screws by equal amounts clockwise (leaner) to give you a drop of 20 RPM. Edelbrock reckon that's the position for best lean idle. It's in the carb owners manual it you have one. I can send you a PDF if you need it.
    The other thing that helps in some circumstances is to raise the idle speed a little.

    This should get you close. Otherwise, you may need to practice your smooth talking charm abilities for discussion with the tester.

    Hope that helps.
    Regards
    Richard

    Dax - Standard Chassis, a boot full of parts, Chevy 383 Stroker and Tremec TKO 600. Time for paint!

  3. #3
    Join Date
    Jan 2006
    Location
    Chelmsford Essex
    Posts
    528
    Agree with Richard a purchase of a vacuum gauge will allow you to set the mixture very close also they are good for fault diagnostics . Just purchased one myself the Gunson's gauge comes with pipe and adapters . This guide might be helpful on adjustment .

    https://www.youtube.com/watch?v=wR_AfQjyT-A

  4. #4
    Join Date
    Jan 2002
    Location
    Woodham, Surrey, UK.
    Posts
    513
    Excellent!

    Thanks chaps - I've just unearthed a vacuum gauge long stored in the garage, and now have a use for it.

    cheers

    B

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