Subframe/frame rail replacement

Discussion in 'Classic Mustang Specific Tech' started by Rusty67, Jun 28, 2009.


  1. Rusty67

    Rusty67 Well-Known Member

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    I need to replace both of the front frame rails on my 67. I am going to be puting in some full length subframe connectors and a cage in the rear only (no full cage). I am thinking of just replacing the frame rails with tublar stock and connecting them directly front to back. Do you guys think this would stiffen up the car more then replacing them with stock frame rails and running subframe connectors ?
  2. 2+2GT

    2+2GT Well-Known Member

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    No, I don't. It would take a LOT of engineering to break even with a properly assembled stock front end, if assembled properly and reinforced with export brace and Monte Carlo bar.

    This 68 GT350 had rotted front rails, and they were replaced with Dynacorn assemblies. The work was done one side at a time to preserve dimensional integrity. These assemblies will cost you $1500 for the pair, a lot less than custom framing would cost. They also feature the 68 1/2 Cobra Jet tower reinforcement, which actually had to be removed for this Shelby.

    68 GT350 Restoration


    [​IMG]

    If you really want to do some reinforcing, add convertible inner rockers to tie the rails together. Much stronger than aftermarket subframe connectors.
  3. Rusty67

    Rusty67 Well-Known Member

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    I forgot to mention that there is no labor cost associated with this project, only materials cost.

    I was going to replace my floor pans first and then move to the frame rails.

    So you think it would be best to put in stock frame rails and then put in subframe connectors ?
  4. 65FBE2

    65FBE2 Member

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    Ditto on the stock rebuild first. Then add in the inner rockers. There are a Couple other ways to go. Mustangs Plus makes a chassis strengthening kit which is close to the convertible reinforcement set up. works great and really stiffens the whole car. I used Miar Racing sub frame connector on my fastback. They are better than most out there because the weld in at two spots in the front and two spots in the rear so as to not create a fulcrum affect. They are also round which is stronger than square tubing once it is bent to fit the shape of the floor. They do limit side exhaust though and cost a Little more than the cheap bolt in ones. If you have the money or talent, do the Mustangs Plus kit
  5. 65FBE2

    65FBE2 Member

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  6. 2+2GT

    2+2GT Well-Known Member

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    The design is not bad, up to a point, the rear end is very good, and the round tube has more torsional strength than more common square tubes, but the front end is poor. If the tubes came forward another foot, ending at the wide part of the rail, it would be far stronger. As it is, it terminates at the weakest point of the front frame rail, adding no strength at at in the front. That portion of the stock rail is so weak you could bend one with your bare hands. Had the connector bridged past that, well, too late now. I would have added the stock 68-70 torque boxes, and run the tube to the front of that. What you have right now is weaker at the firewall than a stock 68 6 cylinder coupe.:(
  7. Rusty67

    Rusty67 Well-Known Member

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    I also have the boss 302 chassis manual which I plan on using as a basic guideline for this project.

    I will be using all tubular stock when I do this.
  8. brianj5600

    brianj5600 Active Member

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    I agree that running the frame connectors a little farther forward would add strength. I ran 2x3 inside the front frame rails. The floor support that most connectors weld to are not very substantial.
  9. Mustang Junkie

    Mustang Junkie New Member

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    You might want to consider adding Convertible Front Torque boxes. I did this on my 66 coupe and it looks great. It should really add to the rigidity.
  10. Rusty67

    Rusty67 Well-Known Member

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    I'm planing on following the boss mustang chassis guide as much as possible. If thats not in there, I'll add it to the list. Looks are my last concern, I want this thing to be a beast on the open track =)

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