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Thread: EFE (Early Fuel Evaporation) Valve

  1. #1
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    Sep 2008

    EFE (Early Fuel Evaporation) Valve

    I'm told that in order for my 1983 GMC 454 to pass smog, I need to install a new EFE Valve. I can't find one at Auto Zone of GM Direct. Can anyone either sell me one, or tell me where to buy one. Thanks

  2. #2
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    leolkfrm's Avatar
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    Mar 2008
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    are you looking for the heater assembly for under the carb? Either way do the dropdown on the NAPA site and you might find it
    NAPA Online PartsPRO SE?
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  3. #3
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    Sep 2008

    Non-electrical EFE

    Thanks for the suggestion. On some later models, there is a heater under the carburetor, but on my 1983 GMC C3500, the EFE Valve is vacuum operated from a TVS in the intake manifold.

  4. #4
    Senior Member
    Join Date
    Sep 2007
    So. NH

    LMC has them (pricey)

    LMC has them. They are on page 123 - around $300. And the TVS that operates it runs about another $50.

    The EFE valve acts like a damper on a wood stove, but exactly the opposite way. It is of the butterfly configuration and restricts the exhaust gas flow in the left side exhast pipe under cold start conditions. This restriction serves to force more hot exhaust gases back up to the underside of the intake manifold... Here read this from Alldata, they explain it better than I can (I am assuming that yours is of the vacuum servo design):

    The EFE system provides a means of rapidly heating the induction system during cold engine operation. Rapid heating improves fuel vaporization, which in turn improves mixture distribution and reduces the length of time that carburetor choking is required. Two types of EFE systems are used, the vacuum servo type and the electrically heated type


    V6 & V8 Engines

    1. Drain coolant until coolant level is below engine coolant outlet housing.
    2. Disconnect hoses from TVS ports.
    3. Remove TVS.
    4. Reverse procedure to install. Torque TVS to 120 inch lbs.
    V6 & V8 Engines
    1. Remove crossover exhaust pipe.
    2. Disconnect actuator rod from valve.
    3. Remove valve from exhaust pipe.
    4. Reverse procedure to install.
    I will try to attach a PDF image - if it is not too large. No problem, it attached.

  5. #5
    Senior Member silverhairdeere's Avatar
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    Feb 2008
    land between the lakes tn

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