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308 Motor Mount Shim

Discussion in 'Technical Q&A' started by pma1010, Nov 30, 2003.

  1. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
    2,559
    Chicago
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    Philip
    I have also searched the old archives but to no success. I have pulled the rear motor mounts on my 308 to cure an oil leak around the studs that hold the mount to the motor. Lots on this in the archives. Permatex #2 solution.

    Separately, the vertical bolt that holds the rear mount to the frame has a large (say 3 - 4 mm thick, 50 mm diameter) washer/spacer between the mount and the frame. This washer/spacer has a 25mm, 1 - 1.5 mm deep recess milled out from the center, into which fits a smaller washer/spacer. One of my mounts has the smaller washer, one doesn't. I don't believe they have ever been apart. Looking at the SPC, I notice (i) motor shims are only on the front engeine mounts, not the rears; (ii) the larger spacer is shown; (iii) the smaller is not.

    This leaves me with two options:
    (i) "leave it alone if it isn't broken": put it back together as it was.
    (ii) add in a new spacer to match its partner.

    Anyone have experience of this? Recommendation?
     
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  3. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    6,999
    Groton, MA
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    Verell Boaen
    IMHO: If the engine is sitting right in the compartment & it sounds like it is, then the shims are probably there to deal with a frame construction irregularity.
     
  4. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
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    Verell
    I am sure that's right, but I think that's the function of the shims shown in the SPC for the front motor mounts. It's just that I can't tell if the rears are shimmed -- if they are, then all would seem to be well, if not, then I am missing a small washer.

    Anyone had these things off the car and can advise?
    Philip
     
  5. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    6,999
    Groton, MA
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    Verell Boaen
    Don't assume there's a problem if a shim isn't installed. Shims are used as needed to make up for production tolerences and won't be there if a particular area meets spec w/o them.

    Remember that the 308 frames are built up of tubing that's clamped & welded. A particular bracket or tube can end up at a slight angle that will need a shim to correct it's location. Other times everything can come out spot on & no shimming is needed.
     
  6. atlantaman

    atlantaman Formula 3

    Mar 31, 2002
    1,726
    Roswell, Georgia
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    Charles
    without the shime the bottom of the bellhousing will hit the frame and the clutch cable will likely run against frame
     
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  8. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
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    Charles, remember, I am recording what was in place. There was no small washer/shim for this mount - the larger shim had the recess and the threaded end of the mount was riding in the recess. No fouling. Nothing in the SPC to guide either. My point is/was, this seems strange, isn't something missing.

    I am sure an omission of the shims for the front motor mounts would cause alignment issues.
     
  9. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
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    Tod at Continental agrees with Verell. Put it back together today. BTW, the recessed side goes uppermost.
     
  10. 4re gt4

    4re gt4 Formula 3

    Apr 23, 2002
    2,279
    Roseburg, OR
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    Hans E. Hansen
    Improper shimming can cause shift problems. My car had to be 'tweaked' a bit - reshimming the mounts - to level the engine and allow smooth shifting.
     

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