Bolt size for engine mounts

Engine, Trans & Driveline

  1. Wietse

    Wietse Well-Known Member

    Messages:
    1,436
    Likes Received:
    560
    Joined:
    Apr 16, 2017
    Location:
    Netherlands
    Local Time:
    7:04 PM
    Hey guys,

    I am going to replace my engine mounts, the old mounting bolts on K-member side are changed out by some metric bolts with lock nuts, thread inside the nut is drilled out so i don't know the size.
    As far as i came these bolts are 7/16"-14 x 3-1/2" long, correct?

    I don't want to modify my new mounts so i need to get a set of proper grade 8 bolts.

    '69 Coronet with 440 engine if it makes a difference.

    Thx!
     
  2. lewtot184

    lewtot184 Well-Known Member

    Messages:
    4,641
    Likes Received:
    2943
    Joined:
    Aug 21, 2011
    Location:
    indianapolis
    Local Time:
    1:04 PM
    all my stuff uses the factory type 7/16"-20 bolts with a locking nut.
     
    • Like Like x 1
    • Wietse

      Wietse Well-Known Member

      Messages:
      1,436
      Likes Received:
      560
      Joined:
      Apr 16, 2017
      Location:
      Netherlands
      Local Time:
      7:04 PM
      Thx lewtot, was quite sure it was 7/16" by rough measure.
      The nut comes welded on the mount, i could add a lock/double nut for extra peace of mind.
      Locally i can get some 7/16" x 4" bolts, i need to shorten them a bit so i can leave some on for another nut.

      I am going to use the mity mounts from Dynatech.
       
    • lewtot184

      lewtot184 Well-Known Member

      Messages:
      4,641
      Likes Received:
      2943
      Joined:
      Aug 21, 2011
      Location:
      indianapolis
      Local Time:
      1:04 PM
      my mounts/brackets don't have nuts welded to them and they are factory pieces. i'd confirm your thread pitch before buying bolts. somebody may have added something to the brackets.
       
    • Cranky

      Cranky Banned Staff Member FBBO Gold Member

      Messages:
      22,754
      Likes Received:
      20632
      Joined:
      Dec 4, 2009
      Location:
      Pasa-getdown-dena Texas
      Local Time:
      12:04 PM
      The rubber mounts (biscuits) do have a nut welded to them.....is that what you are talking about? The 'brackets' that land on the mounts do not have nuts welded to them.
       
      • Thanks! Thanks! x 1
      • lewtot184

        lewtot184 Well-Known Member

        Messages:
        4,641
        Likes Received:
        2943
        Joined:
        Aug 21, 2011
        Location:
        indianapolis
        Local Time:
        1:04 PM
        re-thinking my comments; the isolator does have a nut welded to one end and it uses a 716-14 bolt that passes thru the k-member. the brackets that bolt to the block used 7/16-20 bolts and don't have nuts welded to the brackets.
         
        • Thanks! Thanks! x 1
        • Agree Agree x 1
        • Wietse

          Wietse Well-Known Member

          Messages:
          1,436
          Likes Received:
          560
          Joined:
          Apr 16, 2017
          Location:
          Netherlands
          Local Time:
          7:04 PM
          It's the long bolt that connects the mount with the K-member, bolt B in below picture.
          The nut for that bolt is welded on the metal plate of the mount.

          On the old mount they probably stripped the threads in the past and drilled it out to fit a metric bolt through the hole and secure it with a separate lock nut.
          I want to fit it like it should be but have to get some UNC bolts, the threads on this nut is course thread for sure.

          The brackets that are connected on the engine are still as from factory and do not have nuts or so welded.

          Screen Shot 2019-07-08 at 22.48.15.png
           
          • Like Like x 1
          • Cranky

            Cranky Banned Staff Member FBBO Gold Member

            Messages:
            22,754
            Likes Received:
            20632
            Joined:
            Dec 4, 2009
            Location:
            Pasa-getdown-dena Texas
            Local Time:
            12:04 PM
            Yup, like Lew said, 7/16'ths 14 iirc....and about 3 1/2" long....maybe a tad longer. Nothing much was standard length on cars lol.
             
            • Agree Agree x 1
            • Wietse

              Wietse Well-Known Member

              Messages:
              1,436
              Likes Received:
              560
              Joined:
              Apr 16, 2017
              Location:
              Netherlands
              Local Time:
              7:04 PM
              I did find some replacement bolts, OEM style from R/T specialties on moparshop.de.
              But unfortunately they do not have any stock and have a 2-6 weeks delivery time so i'll opt for something more easy to get.
              Ordered some 7/16"-14 x 4" bolts, will have to shorten them a bit, they are not fully threaded and the treaded part is just long enough after measuring the engine mount bracket, still needs a washer as well to get some more clearance.
              Will be as close as it can get!

              Thx for the help guys!
               
              • Like Like x 1
              • Cranky

                Cranky Banned Staff Member FBBO Gold Member

                Messages:
                22,754
                Likes Received:
                20632
                Joined:
                Dec 4, 2009
                Location:
                Pasa-getdown-dena Texas
                Local Time:
                12:04 PM
                I probably have some here in my bolt buckets.....but no gaarenteeee...lol
                 
                • Thanks! Thanks! x 1
                • Wietse

                  Wietse Well-Known Member

                  Messages:
                  1,436
                  Likes Received:
                  560
                  Joined:
                  Apr 16, 2017
                  Location:
                  Netherlands
                  Local Time:
                  7:04 PM
                  Thx Cranky, i've ordered them and should be coming soon.
                  Shipping is always the biggest problem on this side of the pond :mad:
                   
                  • Like Like x 1
                  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
                    By continuing to use this site, you are consenting to our use of cookies.