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308 carbs

Discussion in 'Technical Q&A' started by tomberlin, Jun 24, 2005.

  1. tomberlin

    tomberlin Formula Junior
    Silver Subscribed

    Apr 9, 2005
    813
    Bethesda
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    tom berlin
    I have a stock 78 308 with a rebuilt motor and stock, reworked distributors. It acts as if there are air leaks at the carbs. Putting my hand over any throat causes noticable increase in revs. Do the throttle shafts leak? Everything else I can check seems secure. Thanks for any help.
    Tom
     
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  3. lusso64

    lusso64 Formula 3

    Apr 12, 2004
    1,535
    Simi Valley
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    David
    yes they do - sometimes badly.

    Carl Jones has sealed bearings available. carl@datasolve.net

    Dave
     
  4. tomberlin

    tomberlin Formula Junior
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    Apr 9, 2005
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    tom berlin
    What seals the shafts when new. Are ther seals there that deteriorated?
     
  5. ham308

    ham308 Formula Junior

    Nov 3, 2003
    358
    NE Switzerland
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    Richard Ham
    There are washers sprung loaded onto the bearings to seal the shaft. I spray mine with chain grease every so often to keep them sealed. It will at least tell you if this is the problem.

    The gaskets to the manifolds also have a reputation for leaking. Again you can spray them for a quick seal test.
     
  6. lusso64

    lusso64 Formula 3

    Apr 12, 2004
    1,535
    Simi Valley
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    David
    They are standard ball races lubricated with grease, that are covered by brass washers. As fuel ends up on the shaft all the time, eventually the grease is washed away, and the brass washers don't really do much.

    The replacement bearings are sealed units, so the grease never gets washed out, so the problem never arises again.

    I used to struggle to get the carbs synched and tuned, but after replacing the bearings, it was a one hour job, and it held the tune.

    Dave
     
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  8. docweed

    docweed Formula Junior

    Dec 8, 2004
    452
    Morgantown,WV
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    Chuck Stewart
    You might try spraying carburator cleaner in areas that can leak to see if the engine RPMs increase. If so that area may have a leak. Use the tube that comes with the can to keep the spray confined to a small area and avoid getting it into the carb throat.
     
  9. tomberlin

    tomberlin Formula Junior
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    Apr 9, 2005
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    tom berlin
    Thanks to all for the help. I had done the spray test with significant rpm change, but was told by one of the popular parts suppliers that there were no seals.
     
  10. ham308

    ham308 Formula Junior

    Nov 3, 2003
    358
    NE Switzerland
    Full Name:
    Richard Ham
    #8 ham308, Jun 25, 2005
    Last edited by a moderator: Sep 7, 2017

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