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Torque recommendations?

Discussion in 'Technical Q&A' started by FamilyCar, Oct 11, 2010.

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  1. FamilyCar

    FamilyCar Formula Junior
    Rossa Subscribed

    Sep 26, 2007
    790
    Seattle, Wa
    Full Name:
    Peter Goodall
    #1 FamilyCar, Oct 11, 2010
    As I reassemble '87 Mondial after replacing the timing belts, I'm trying to do everything by the book. There are of course certain fasteners that do not have a specified torque. Out of curiousity, I looked online for torque specifications by fastener size.

    An example of what I found: The recommended torque for an M6X1.00 Bolt is 9.5Nm (about 7.13 ft-lbs).

    A number of questions follow from this:

    1. Would a nut on a stud be different, and if so how much? I haven't found this anywhere.

    2. The 9.5Nm specification seems very loose to me--is this really correct? Without the torque wrench I'd make it significantly tighter to feel right.

    3. The fasteners were quite tight when removed. Sure they'd been on there a few years, but they aren't especially dirty or corroded. I have to believe they were put on to more than 9.5Nm.

    4. If the 9.5Nm seems reasonable, should I dab on some locktite? There wasn't any on these particular fasteners before.

    5. The 9.5Nm is for a grade 8.8 fastener, it jumps to 10.5Nm for a 10.9 fastener. There are no grade indications on the nut that I can see. Which would the Ferrari use?

    Any feedback is greatly appreciated. Note--I'm using a small wrench that reads in in-lbs and Nm that I believe is quite accurate.

    Regards,

    Peter
     
  2. Chiicago

    Chiicago Rookie

    Oct 6, 2010
    14
    #2 Chiicago, Oct 11, 2010
    There is a very high percentage that the bolt in question is a grade 8.8

    Torque for your bolt is 12.85 NM

    N/M x .7376 = LB/FT

    LB/FT x 1.3558 = N/M

    Torque for: (in case you find it to be different)
    grades 5.8 = 8.14 NM
    grades 9.8 = 13.92 NM
    grades 10.9 = 17.78 NM
    grades 12.9 = 20.78 NM

    Hope this helps!
     
  3. 166&456

    166&456 Formula 3

    Jul 13, 2010
    1,723
    Amsterdam
    #3 166&456, Oct 11, 2010
    Last edited: Oct 11, 2010
    9Nm is correct for me.
    Example, cam bearing torque is also 9Nm on most Ferraris where they use 6mm bolts. It seems solidly enough for me, not loose by any means, and on such places I follow the book religiously, since the head was line/bored with that torque. Overtightening will lead to bearings getting oval. Not good. The same goes for the cam covers, as they can warp if torqued down too much. Remember this is only a 6mm bolt. The maximum recommended torque a fastener is allowed to take does not necessarily mean it is also wise to use that, there might well be other factors. My opinion is not to try to outsmart the engineers on this one. Follow the book. It is possible the previous mechanic did not use a torque wrench.
    Torque on studs is likely to be the same but again / follow the book. Your car became 23 years of age using those torque settings...
    What range of torque wrench are you using? Make sure it goes down to at least 5 to get some accuracy, I use one with a range of 4-25Nm I believe.
     

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