stiffening rear frame rails ...make this sense ??

1968 -1970 Mopars

  1. acii

    acii Well-Known Member

    Messages:
    51
    Likes Received:
    13
    Joined:
    Mar 14, 2020
    Location:
    Germany
    Local Time:
    11:14 AM
    Hy all

    i have to replace both rear frame rails on my 70er charger.

    I am thinking about stiffening the rails.. as i saw some threads about stiffening the torsion bar crossmember...
    Would be a kind of boxing the rails ....
    the rails originally are not making the strongest appearance ...pretty flimsy

    Does it make sense ??

    THanks for advice !!
    Cu
    Achim
     
  2. 493 Mike

    493 Mike FBBO Gold Member FBBO Gold Member

    Messages:
    3,218
    Likes Received:
    3536
    Joined:
    Dec 25, 2011
    Location:
    White Cloud, MI
    Local Time:
    5:14 AM
    No reason you can't. You could stitch weld a horizontal strip of steel maybe 1-2" below the flanges, even use a "T" shape piece to gain more strength. Do you need extra strength? How much horse power are you planning?
    Mike
     
  3. Kern Dog

    Kern Dog FBBO Gold Member FBBO Gold Member

    Messages:
    20,999
    Likes Received:
    54605
    Joined:
    Apr 13, 2012
    Location:
    Granite Bay CA
    Local Time:
    2:14 AM
    Pointless for a stock or near stock power level. The rails are essentially boxed anyway since they are 3 sided with a floor pan closing the 4th side.
     
    • Agree Agree x 5
    • F4R/T

      F4R/T Well-Known Member

      Messages:
      1,090
      Likes Received:
      1376
      Joined:
      Jun 17, 2020
      Location:
      Illinois
      Local Time:
      4:14 AM
      I would say leave em alone ,
      What is your game plan that you need to
      Stiffen them unless they are soft from rot issues? Now putting in sub frame connectors and torque boxes definitely if your going to push it hard...
       
      • Agree Agree x 2
      • acii

        acii Well-Known Member

        Messages:
        51
        Likes Received:
        13
        Joined:
        Mar 14, 2020
        Location:
        Germany
        Local Time:
        11:14 AM
        thx for ur advice..

        horsepower-wise i dont wanna go for a big number .. something around 350 - 400...(more or less stock).

        I was just thinking ... also like the famous example to add some stiffening plate to the lower control arm (front suspension)..

        But it looks like to be pointless ... so i will most likely drop that idea :) or maybe add one ore two plates for my good conscience

        CU
        Achim
         
        • Agree Agree x 1
        • RT68440

          RT68440 Well-Known Member

          Messages:
          406
          Likes Received:
          418
          Joined:
          Mar 8, 2016
          Location:
          Akron, Ohio
          Local Time:
          5:14 AM
          I'd be leery of doing a bunch of unnecessary welding on the rails with the 4th side opened up. It may move around on ya and cause more harm than good...
           
          • Agree Agree x 1
          • Hey-O

            Hey-O FBBO Gold Member FBBO Gold Member

            Messages:
            9,241
            Likes Received:
            26115
            Joined:
            Nov 21, 2018
            Location:
            St Charles Mo
            Local Time:
            4:14 AM
            It would take more than 400 horse power to twist a frame that was built to handle more than that from the factory. Everything is made to give a little, changing that would make the car feel stiffer. I've never done it to a mopar, but I have other cars and could feel it.
             
          • Superbee Sean

            Superbee Sean Member

            Messages:
            12
            Likes Received:
            12
            Joined:
            Apr 25, 2021
            Location:
            Argyle, NY
            Local Time:
            5:14 AM
            I have reading on here about the Torque Boxes. Your profile pic caught my attention since I am an Aircraft mechanic and we operate a small fleet of Hueys. I am saving a 1968 Super Bee (383 4 speed) which, does not have them installed. I am on the fence with installing them. I know, from our Hueys, we make airframe repairs and stiffen up one area, and soon enough we are fixing another area. Would this be the case if I were to go that route on this car? I don’t plan on racing the car, but do plan to smoke the tires......occasionally...... To torque box or not torque box......that is the question?
             
          • 493 Mike

            493 Mike FBBO Gold Member FBBO Gold Member

            Messages:
            3,218
            Likes Received:
            3536
            Joined:
            Dec 25, 2011
            Location:
            White Cloud, MI
            Local Time:
            5:14 AM
            With a manual transmission I think it is a good idea. Not to hard to fabricate/install either.
            Mike
             
            • Like Like x 1
            • Thanks! Thanks! x 1
            • 70chall440

              70chall440 FBBO Gold Member FBBO Gold Member

              Messages:
              2,641
              Likes Received:
              3812
              Joined:
              Feb 11, 2018
              Location:
              Yelm, Washington
              Local Time:
              2:14 AM
              I would say that it isn't necessary even with a manual car or even a moderately powerful engine. The rear frame rails are boxed in (as stated) and connected to the trunk pan which is connected to the tail panel and quarter panels, Dutchman panel, roof, etc. so the transfer of energy under load is pretty well transferred throughout the car. That said (and if you are concerned about it) it would not hurt to put some spot welds into them or even put some 4-6" runs of welds along the sides where they meet the floor pan.

              These cars are as I am sure you know spot welded and back in the day it was the sum of all of the spot welds that provided the rigidity of the car (which was/is not all that great). If you want the car to be stiff (read handle) welding up the seems and putting some really good welds on all of the cross members and rear frame rails really helps. You would be surprised at how well this works and how much stiffer the car will get. You couple this effort along with torque boxes and subframe connectors and that car will be solid.
               
              • Thanks! Thanks! x 1
              • biomedtechguy

                biomedtechguy Accelerati Rapidus Maximus FBBO Gold Member

                Messages:
                24,666
                Likes Received:
                35612
                Joined:
                Mar 28, 2014
                Location:
                South Louisiana
                Local Time:
                4:14 AM
                Since I was having the front K-member and suspension replaced with QA1 stuff, rear leafs replaced with Calvert split mono leaf springs and sliders, I figured it was a good time for front spring bolt reinforcement plates in front and behind the factory sheet metal mounts, 4 torque boxes, and subframe connectors, since I was upgrading to the MAX all of my drivetrain components. This will help resolve a long standing launch traction problem, along with the Assassin traction bars. It will help now, and it's all ready for the 541 stroker I'm working on having built.
                Oh, and it's a manual transmission car too...
                 
              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.