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BB clamshell unlatching

Discussion in 'Boxers/TR/M' started by OLDBENZ, Oct 24, 2020.

  1. OLDBENZ

    OLDBENZ Rookie

    Dec 7, 2016
    12
    Greetings!

    I have a recently acquired rebuilt 512BB.

    I noticed that the left side latch of the front clamshell bonnet was continually unlatching. The supplying specialist had a go at adjusting it with other items on my snag list but it is still unlatching, albeit slightly less frequently than before.

    Is there a trick to getting the adjustment as it should be? I am guessing that it unlatches because the cabling is too tight but that is just a guess. I am now noticing a number of other BBs have their clamshells unlatched (always) on the left so wonder if it is a common issue.

    Many thanks.
     
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  3. pshoejberg

    pshoejberg Formula 3
    Silver Subscribed

    Dec 22, 2007
    1,332
    Denmark
    Full Name:
    Peter H
    I have never heard anything generally about latch problems with BB or BBi's. That said, it is a delicate system that is sensitive to wear and tear and so are all the latch systems on older Ferrari's such as 308's and others. When I repair old latch systems I always change out the wires and check/swab out all the nylon bushes in the pull system. I clean out the guide piping and grease or lube as necessary. Then I check the latches for wear and change out if excessive wear is observed. If the car is straight and still have the original lids then adjustment of the system should be straight forward and you eventually will have a effective and trustworthy lock system. No hocus pocus here.

    Best, Peter
     
  4. OLDBENZ

    OLDBENZ Rookie

    Dec 7, 2016
    12
    Many thanks for the advice.

    Best wishes.
     
  5. Bknblk

    Bknblk Rookie

    Apr 30, 2019
    17
    Full Name:
    Josh Toby
    I have had recent experience with the opposite problem here: my latches have been a bit resistant to opening. I completely agree with cleaning the system and replacing any worn parts, but I suspect you might have some luck with adjusting the set screws which keep the latches under tension.

    My recommendation is to use a pair of vise grips (set tension to firmly clamp) to clamp on the braided cable below the latch about 1-2mm from where the ferrule is presently clamped on the cable. Use a small allen wrench to loosen the set screw in the ferrule and slide it the 1-2 mm to where the vise grips are clamped (it will likely do this spontaneously since it's under tension). Re-tighten the set screw firmly, remove vise grips, and close the cover to test the setting. Repeat until desired release tension at interior handle.

    Good Luck!
     
  6. OLDBENZ

    OLDBENZ Rookie

    Dec 7, 2016
    12
    Thanks for the advice.
     
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  8. ross

    ross Three Time F1 World Champ
    Silver Subscribed Owner

    Mar 25, 2002
    32,058
    houston/geneva
    Full Name:
    Ross
    the left side of mine is always a bit fiddly.
    i have to make sure to fully pull the latch, and then i have to lift the hood and jiggle the whole thing a bit for it to come free.
    after you have done it 5000 times you get the hang of it. :)
     
  9. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    6,443
    southwest germany
    Full Name:
    romano schwabel
    and after the next engine out service the clamshell is fixed a little different and all begin from new for the next 5000 ;)
     
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  10. soshry

    soshry Formula Junior
    Silver Subscribed

    Jul 27, 2004
    601
    New Jersey
    Full Name:
    Scott
    Fantastic question, I have been battling this problem since we restored my car. The tolerances needed to have the ring fit exactly into the latch is down below a mm. I finally created a technique that allows me to see where the ring is rubbing in the latch so the ring can be adjusted through subtle bending, twisting and undoing the screws to either lengthen or shorten the ring. It is a combination of all this that will allow the ring to sit perfectly into the latch.

    I use blue painters tape and wrap it around the ring, only one pass so the tape just covers the ring once. Then put the bonnet down, push, reopen. The thin tape will tear where it is rubbing on the latch and show you where the high points are. Then, using the mentioned adjustments above you keep bending/moving the ring, repeating the tape application and closing the bonnet until you will eventually see no more tear on the tape.

    It worked perfectly for me and now finally all my bonnets close properly.

    If you need a pic let me know and I will take one.
     
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  11. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    6,443
    southwest germany
    Full Name:
    romano schwabel
    good idea with the tape :)
    I used paint until now and waited until next day. next time will try this job also with tape
     
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  13. pshoejberg

    pshoejberg Formula 3
    Silver Subscribed

    Dec 22, 2007
    1,332
    Denmark
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    Peter H
    I adjusted mine with the inner fenders removed....Very easy but not an option for an ordinary adjustment unless you are doing it in combination with a complete restoration. One trick for adjustment in lateral direction is to loosen the bolts a little on the upper ring hatches so they find the the neutral point them self when the lid is closed. Also remember that the latch itself can be shimmed on the backside should it be necessary. It shouldn't be necessary to bent anything.

    Best, Peter
     
  14. DonB

    DonB Formula Junior
    Rossa Subscribed

    Nov 11, 2003
    386
    Florida
    Full Name:
    Don Bartz
    FWIW

    There could exist the situation that the rubber trim, that the deck lid rests/seals on, just forward of the cowl and that curves downward, might sit too high. The rubber is mounted over a thin steel form that might need to be trimmed down a bit to allow popper seating of the deck lid and hence the latch.
    Remember, these cars were kinda hand made and the left side isn't always the same as the right.
     
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