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Thread: 47 exhaust manifold question 320

  1. #1

    47 exhaust manifold question 320


    Upon further examination, I don't appear to be leaking from the exhaust manifold-to-engine area, but rather where the manifold attaches to a short "T" section before the exhaust flange. There seems to be a round seal there.

    What is this part called and where can I get one?

    Thank you for your help.

    1947 Roadmaster 4 door

  2. #2

    Re: 47 exhaust manifold question 320

    Whoops! Bill Stoneburg might have answered my question below with an addition to my earlier post.

    If this "T" is called the Center Section, then there is no seal, but rather a high temp sealer. Is that right?

    I was trying to have all of the necessary parts together before starting the job so I don't know if it's cracked or not. If it is, any advice on a source for a new Center Section. Also the sealer?

    Thanks again,

  3. #3

    Re: 47 exhaust manifold question 320

    On the large series engine for the Roadmaster, there are three pieces to the exhaust manifold. You mention the "T section that bolts to the exhaust flange". This could be the valve body or "hot box" which bolts to the intake manifold, center section of the exhaust manifold and the exhaust pipe via the exhaust flange. The valve body contains a flapper valve that allows exhaust heat to reach the base of the intake manifold during warm-up of a cold engine. When the engine is hot, a thermosthatic spring on the flapper valve shaft allows the flapper valve counterweight to move the flapper valve to a position that channels the exhaust gases out to the exhaust pipe.
    There is a gasket at the bottom of the valve body to the exhaust pipe flange that may be your problem. Generally the 3 sections of the exhaust manifold are a friction fit and no heat sealer compound is used. The center section of the exhaust manifold uses a triangular shaped gasket and a steel ring where it bolts to the valve body. This could also be a source of the leak.
    A shop manual should have an illustration of this arrangement.
    Joe, BCA 33493

  4. #4

    Re: 47 exhaust manifold question 320

    Thanks, Joe.

    The exhaust leak is definitely between the forward exhaust section and the center section and blowing forward. Exhaust is escaping only at about a 40 degree arc where there seems to be a goodly bit of space (say 15 thousands) between the outside diameter round pipe of the forward section and the larger inside diameter of the center section. I see no obvious crack.

    With such an array of new products available, could not some high temp sealer be squirted in the leaking area and allowed to cure. I would rather try something like this before tearing into it as I have a tendency to make things worse.

    Any suggestions?

    Thanks again,

  5. #5
    Early Buick Numbers Guy
    Join Date
    Feb 2006

    Re: 47 exhaust manifold question 320

    Dear Sherlok:
    Keep in mind that the temperature of this joint is above 700 degrees F, when the engine is running you down the road at 60 MPH. Half measures don't get things done! Yes, I know the parts cost 400-500 dollars. Yes, I know it's a scary sounding project. Ir really isn't that bad. Use plenty of penetrating oil, lots of patience, and common sense. Follow the instructions Bill Stoneberg forwarded in another thread.
    Regards, Dave Corbin

  6. #6

    Re: 47 exhaust manifold question 320

    Thanks David,

    I'm really into now! See recent post.

    Appreciate your good advice.


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