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  1. #1

    Default canister on driver side exhaust manifold

    One more question. Their is a canister that looks like a vaccumn canister that has a connection for a line. What is it for & what connects to it. This is on the back side of drivers side exhaust. Thanks! Fran

  2. #2

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    Pictures? Year? Engine?

    Sounds like it might be the vacuum reserve canister. That helps to keep/smooth vacuum at idle. That's because the cam/engine is "lopey" (https://www.corvetteforum.com/forums...ivability.html , https://ls1tech.com/forums/generatio...-ness-cam.html ).

  3. #3

  4. #4

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    If your car is a 85 GT with the M code engine it’s the vacuum controlled heat riser valve. Used to help speed engine warm up.

  5. #5
    FEP Super Member xctasy's Avatar
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    From memory, its a vacuum canister called a Heat Valve. Heat VLV
    See qikgts Vaccum Emissions Control Info diagram CHB E5AE_9C485 for his 1985 Hi Altitude 4V GT.

    Heat VLV.


    Its a normally open canister which controls the exhaust diversion to the primary light off catalyst.

    boboli photoed it, its the item on the top of the picture that looks like a waste gate actuator.



    http://vb.foureyedpride.com/showthre...1985-Emissions
    http://vb.foureyedpride.com/showthre...-exhaust/page2


    The earlier 83 and 84's with 4-bbl carbs (not the CFi's) had no tubing headers, and had another kind of secondary heat stove which blocked off one side of the exhaust to pre-heat the primary light off oxidation catalyst.

    Its some times called a flapper valve too. The 85's have a bigger 2.75" one, not the earlier 2.375".

    http://vb.foureyedpride.com/showthre...23#post1656823


    Quote Originally Posted by boboli View Post
    Since you asked about the heat riser, I found one of the 85 ones I have. I think I tossed the other long ago. There are 2 on ebay right now( 1 used and 1 new) that look exactly the same.
    from the rear


    from the engine side


    the label on the vacuum canister has long since been destroyed, so I can't read any #'s. The label almost looks to have a bluish color, but I can't say if that is original or just from time. The original on ebay has a red sticker. Maybe they are color coded to size? The only cast # on the valve body is a #4 right at the corner, near the vacuum canister.

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