Frame rails repair metal

Chassis, Suspension and wheels

  1. SixBanger

    SixBanger Well-Known Member

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    Looking if possible to safe/repair the left front frame rail.
    Last weekend the car jacked up at this place. And this place turned out to be worse ... But that can be repaired. I think.

    I saw on a old thread here linked to repair sheetmetal for FMJ on autorust.com. But they stopped producing some of the parts for our mopars.
    Repair frame rail with own sheetmetal? And or adding a frame connector from USTC Motorsports?
     
  2. Oldiron440

    Oldiron440 Well-Known Member

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    The proper way to repair rust is to replace the rusted metal. Replace the frame rail with a solid part.
     
  3. BudW

    BudW Moderator Staff Member

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    I would agree with him.
    There are other ways - but best way is to replace with a solid part.
    Most M-bodies (generally) do not have the rust problems that F’s have. Not sure if use of better metal, better chemicals before paint or what/why. The ’88-89 M’s used mostly galvanized steel.
    I would find some M-body frame rails and have shipped to you. F Body Deconstructor might be a great source.

    The frame rails are the same in F and M’s (as far as I can remember) – but might be slightly different for J’s (maybe). That said, there might be some minor brackets that differ over the years (like brake line brackets, etc.) so some small items might need to be carried over.

    Putting a cap over an already rusted beyond use frame rail is scary to me.
    BudW
     
  4. SixBanger

    SixBanger Well-Known Member

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    Yes you two are right, that should be the way to attack the rust.
    The car was in okay condition since recently for a new MOT. This will expire soon and some other spots.
    This afternoon I had put the car on the bridge in the local garage. He advised me to weld a plate over it, and let the car go.
     
    Last edited: Dec 7, 2019
  5. Aspen500

    Aspen500 Well-Known Member

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    What I did with my car was cut out the rotted portions of the frame rail (in my case, left side only) which was only on the rear portion behind the suspension and, fab/weld in new pieces of similar gauge steel. Then, I fully welded caps over each front subframe rail, mainly for chassis stiffening than anything else.

    I bought the ART caps and was unimpressed. Looked like they were made by an 8 year old and it was their first time using a MIG. A few hours of welding, grinding and reshaping, they became what I thought I was buying in the first place. Hindsight says, it would have been less work to get flat stock and make them myself. Thought buying them pre-made would save some time. Boy was I wrong!:eek:

    Question: MOT?
     
  6. Oldiron440

    Oldiron440 Well-Known Member

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    I've done complete frame rail replacements and as ominous as it frist appears it's actually easier then trying to scab in a repair. It's more of a mindset , off with the crapp and on with the good.
     
  7. SixBanger

    SixBanger Well-Known Member

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    MOT is kind like a two yearly test for a car. For safety reasons it has to be checked by a garage.
     
  8. Rattle Trap

    Rattle Trap Well-Known Member

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    Whole rail is only 50 spot welds and a bunch of measuring. If you go that route, cut the old rail from the inner fender then remove the welds from the inner fender after you've gotten complete access. The MIG welds in the upper control arm area can't be cut properly with a rail in place.

    20160201_202425.jpg
     
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  9. Rattle Trap

    Rattle Trap Well-Known Member

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    If you choose to stub in a partial, I do it behind the K-member with rosette welded fish plates inside the rail. One on the inner side of rail attached to the existing forward section. One attached to outside vertical of the new lower piece. Slip them together tack a couple rosettes and double check all the measurements then weld all holes and seam solid along with new floor pan and trans crossmember spot weld replacement.

    20160122_182238.jpg
     
  10. Aspen500

    Aspen500 Well-Known Member

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    This isn't really a frame rail repair thing but, what I found helps chassis stiffness quite a bit is to fully weld the inner panels to the frame rail, unless you're going for a perfect restoration. On my car there was a grand total of 4 spot welds on the left side and 3 on the right and one of those was broken loose from metal fatigue (not rust). Pretty much not even attached. When repairing or replacing a subframe rail you "might as well" "while you're at it" and that is where the snowball starts:p
     
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  11. Oldiron440

    Oldiron440 Well-Known Member

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    Ok what did you use for the frame connectors? I used 2" heavy wall steel, I can jack the car from the middle of the body using the frame connectors.
     
  12. Rattle Trap

    Rattle Trap Well-Known Member

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    That guy on right side front body in the late 70's must have been a real drunk. Usually you're lucky to get any spot welds in the inner fender apron to the firewall. And if you did, they're broken from metal fatigue after he didn't lay them in long enough and the whole thing flexed til they broke. Of course he didn't have to be very good at his job since the passenger fender stampings are junk and rarely ever line up to a door anyhow.
     
  13. SixBanger

    SixBanger Well-Known Member

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    Thanks guys for info! I think I should go for the partial repair. To replace the original frame rail to flooring (that T-section is bad, to rear it is more solid). But this should be taken more time before getting MOT.
     
  14. JMGray

    JMGray New Member

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    I got an 81 Mirada with this left frame rail rot issue. I was disappointed to see that ART discontinued their safe-t caps but relieved to see that they were garbage and a homemade replacement is a better more economical route. My question is; do I have to support my car in any way when cutting out the rusted section. I haven't gotten down there to measure how much is rotted out but i'm guessing that it around 12" or what Rattle Trap has posted. any tips and tricks to help me out would be greatly appreciated
     
  15. Rattle Trap

    Rattle Trap Well-Known Member

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    If you're going to chop a rear rail section out for replacement, Leave the K-member in place to maintain the side to side critical dimension while a rail is incomplete. Also, a rear section of a pass rail is much easier to get than a driver side. And they're all the same stuff back there. It's the forward sections that make the difference. Since I don't have a frame rack, I have shot my floor points according to the frame layout plan with a laser level to know if compensation is needed for unlevel concrete. It's not perfect no matter how good your garage floor looks. Mine is off by up to 5/16" from one spot to another. All this matters and you need to compensate for it. But thankfully friends always have tools and skills. I just use various thicknesses of plywood to level floor areas against the highest one. Once I have it mounted level at the trans crossmember and the rear height measurements match, I go ahead and remove the rail section and replace. I use basement screw jacks made into jack stands for the forward section so I can make small height adjustments under the K. You could as easily do it with a couple floor or bottle jacks. You want to have the front draped loose when you measure the rest of the chassis for height, because when you reapply the weight of the vehicle to the front wheels it is going to flex upward. You need to compensate for that in the front height measurements. Don't make them completely equal to the original jig heights as listed on that diagram. Understand that you're also trying to match whatever you have on the other side without making the whole front clip cockeyed. I screw the replacement side up into place 1/8" down from being correct as compensation typically, although I've seen higher mileage cars drape down over 1/2" when the front becomes unloaded by supporting the trans crossmember, while they hang complete. You need to be conscious of the up and down relationship as also applied to wear and tear of what remains to keep it all lined up when finished. It's all geometry and you're changing the hypotenuse with everything you do. Geometry is the simplest form of advanced math. It's not that hard. It's easier than long division. We aren't really dealing with Trig as long as we don't remove the K-member. If the pass side comes down deep, leave it deep and make the driver side low, but not that low because you realize that it's going to be significantly less flexible after your repair than your old original side is. You want them to come up about even, but it is always best if the driver side is just a little lower to offset engine torque. But if you make it as low as the pass side might drape down to when unloaded, it's going to be Way low after putting weight back onto the wheels. Everything has a range of motion, even if you think it's solid. What you're doing is creating the strongest point of a 40 year old metal assembly. Just keep that in mind. All the rest has wear and tear on it and make your best guess based on what your particular car does in loaded on wheels and unloaded to centrally supported measurements.

    But if this all sounds too technical or daunting just remember, these things were slapped together on an assembly line the same as all other vehicles of the time, and prior. Made of missed welds and seam sealer, and there isn't really much of anything you could do as an enthusiast who is carefully checking and considering everything, fitting and trimming before welding, that could ever be as bad as what came off that line when somebody was timed for how quickly they could slap fresh stampings into a jig and start welding them up. Your best guess is still going to be better than it ever was before. Because you'll take a minute or a day to think about it and all the time that's elapsed and what that assembly has been through in that intervening time first.

    If I can do it, you can. I'm just a guy who wasn't afraid to screw it all up long enough to prove to myself that I hadn't. Then did it again and again.
     
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  16. JMGray

    JMGray New Member

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    This is a brilliant response thank you for all the information. When I first started reading it sounded rather daunting but the last sentence cleared everything up that I need to basically, take my time, measure twice and not wear my butt as a hat.

    I'm going to start another thread soon and post pictures and progress there. thanks again
     
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  17. SixBanger

    SixBanger Well-Known Member

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    I don't mater if you post your progress on this thread if you want that.
     
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