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Thread: 1973 TR6 brake booster hose

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    Jedi Hopeful sundown's Avatar
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    1973 TR6 brake booster hose

    I'm trying to find out why the idle is so high without the idle screws even making contact if there is a crack in the booster line would that effect the idle Thanks for any help

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    Great Pumpkin NutmegCT's Avatar
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    Re: 1973 TR6 brake booster hose

    --> vacuum leaks mess up the idle speed. Large vacuum leaks yield a *fast* uncontrollable idle.

    (I speak from experience ...)
    Tom
    Mac & Phyllis Take a Trip: http://nutmegflyer.com/trip-details-daily-updates/
    History: 1976 MGB, 1959 Triumph TR3A, 1960 Mercedes-Benz 190b, 1958 Rambler American, 1953 MG TD.
    Next? who the heck knows!

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    Great Pumpkin - R.I.P TR3driver's Avatar
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    Re: 1973 TR6 brake booster hose

    Have you removed the vacuum retard? If so, the linkage to the float bowl vent valves may be holding the throttle open. Another place to check would be the throttle bypass valve; a cracked diaphragm will allow lots of extra air in.

    Yes, a crack in the booster line, or in the booster diaphragm, will have a large effect on idle. It creates a huge vacuum leak.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Jedi Hopeful sundown's Avatar
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    Re: 1973 TR6 brake booster hose

    If it turns out to be throttle bypass could I block off passages? Also is there a nominal setting to start with on the adjusting screws to get the valves in the ballpark. Thanks

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    Yoda poolboy's Avatar
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    Re: 1973 TR6 brake booster hose

    I see you have a 73 car...if your carbs are also 73's then it might be a fairly common problem that affects the idle setting.
    The controls for the valve that transitions the location of the vent for the float chamber was experimental in 73. It was changed for the better in 74 and remained the same throughout the TR6 run.
    73 version shown here:

    Look for interference with the throttle stop lever.
    Ken @
    kencorsaw "at" aol.com
    DRIVE 'EM IF YOU GOT 'EM

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    Jedi Hopeful sundown's Avatar
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    Re: 1973 TR6 brake booster hose

    Thanks for all the input and yes poolboy the carbs are 73 it was a stock car when I bought it. Is there any remedy to correct this problem I hope? I did cap off the distributor no vacuum line also capped of the inlet tube under the rear carb andthe float chamber lines are off that go to the charcoal canister.

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    Yoda poolboy's Avatar
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    Re: 1973 TR6 brake booster hose

    You really need to observe what's happening to the throttle stop lever as you manipulate it.
    On several of the 73 cabs that I've rebuilt I have simply removed the 'c' clip and removed the arm that operates the spring loaded plunger (with the owners knowledge).
    You need make sure that the spring loaded plunger is fully extended.
    Then, you will have a carb similar to the pre 73 carbs in that ALL the ventilation of the float chamber will be thru the brass lined port in the carbs' air box mounting flange..
    You will, however, not have use of the Anti Run-on Valve that came into existence post 72.. You probably don't need it with proper tuning and good gasoline.
    Ken @
    kencorsaw "at" aol.com
    DRIVE 'EM IF YOU GOT 'EM

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    Great Pumpkin - R.I.P TR3driver's Avatar
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    Re: 1973 TR6 brake booster hose

    My Stag has the same mechanism, and the same problem (for the same reason). Once I realized the problem, it was easy to bend the little metal clip (the black square under the screw head in Ken's photo above) to get enough range to adjust the bowl vent properly. That would have kept the ARV working (if I had an ARV).
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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