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Thread: Heat riser valve on 78 304

  1. #1

    Default Heat riser valve on 78 304

    What is the purpose of the heat riser valve on the 304 series engines. I was assuming it was for some sort of chocke control?

  2. #2
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    Quote Originally Posted by Kmk1605juggalo View Post
    What is the purpose of the heat riser valve on the 304 series engines. I was assuming it was for some sort of chocke control?
    Yes, if you mean the tube that goes to the air cleaner. Air restriction.

    If you mean the flapper between the exhaust manifold and the pipe on the right side, it diverts all of the exhaust from the right side through the manifold into the other pipe so that the intake warms up more quickly. The propane intake manifold gasket has this port blocked off.

    These are year specific smog devices. All SV series engines have them during those years, or not.
    Allan E.
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    Quote Originally Posted by Allan E. View Post
    Yes, if you mean the tube that goes to the air cleaner. Air restriction.

    If you mean the flapper between the exhaust manifold and the pipe on the right side, it diverts all of the exhaust from the right side through the manifold into the other pipe so that the intake warms up more quickly. The propane intake manifold gasket has this port blocked off.

    These are year specific smog devices. All SV series engines have them during those years, or not.
    Doesn't the flapper in your exhaust just make your manifold heat faster so your hot air riser tube works better. I doesn't "divert" anything really because nothing is hooked up to the flapper it just blocks the gases.

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    Quote Originally Posted by skierman View Post
    Doesn't the flapper in your exhaust just make your manifold heat faster so your hot air riser tube works better. I doesn't "divert" anything really because nothing is hooked up to the flapper it just blocks the gases.
    There is a passage through the exhaust manifold expressly for this purpose. Diversion to the other side. It heats the manifold more quickly.
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

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