Frame Rails

Discussion in 'Body Restoration' started by Tallguy2o0o, Sep 17, 2004.

  1. Tallguy2o0o

    Tallguy2o0o Veteran Member

    Messages:
    429
    Likes Received:
    0
    Joined:
    May 25, 2002
    Location:
    Poughquag, NY, USA
    My car just got running and exhaust done, and im now told that my rear frame rail is shot...not good i know. How much is it gonna cost me to get it replaced. is it worth it? i love this car so to me i think it is, but what do you guys think?
     
  2. Dave Semko

    Dave Semko Member

    Messages:
    72
    Likes Received:
    0
    Joined:
    Sep 12, 2000
    Location:
    Bowling Green, OH
    Anything is possible :)

    I've put several new rails in second gen cars - the decision about if it is practical or not depends on the amount of rust, the location of the rust, and how much resource you are willing to invest.

    When you have a chance, tell us the year and location of the rust. We might be able to give you some better advice.

    Generally, replacing the rails is big job - and requires a fair amount of disassembly before you can think about any metal work. When removing the old rail you'll need to pull the rear interior, the gas tank, and all the suspension from the side that requires replacement.

    A key to success is to support the car real well before taking out the old rail. If you are fortunate enough to have a lift, and a plasma cutter the project is not so bad... if you have to do the work with the car on stands, using a air saw and grider it is misery!

    One approach to supporting the body is to make a jig out of square stock and plate, that will attach to the body just before and just after the rail. This helps keep the rear section from 'springing' or 'drooping' when you take out the old rail. If you are working on a lift it is pretty easy to use a pair of tri-pods, tall jack stands - or even some good 4x4's to support the body. What ever you use, be sure it is sturdy. Don't even think about taking the rail out of the car without supporting the body - - it will be a disaster!

    Before you take the rail out of the car make a diagram with some careful measurements. Knowing the distance between the rails will be critical during reassembly!

    When removing the rail, a plasma cutter is the fastest and safest - and since the heat is localized and well controlled you can avoid making a mess of the trunk floor and rear panel. If you don't have a plasma cutter - rent one (of make friends with some one that does :) ). It is best to cut the side of the rail, and leave the flange attached to the floor.

    Once you have the major frame rail section out of the way - it is some time consuming work to take out the flanges from the old rail. I've been successful with a spot weld drill (Eastwood), but odds are high you'll end up missing at least a few. A chisel and hammer will usually get you through the little welds that you miss.

    Normally after you remove the flanges you have to grind off the remaining metal from the old spot welds. This allows the new rail to sit flat against the floor.

    Assuming you don't loose all your patience by this point - - the rest of the job is relatively easy. I usually spray the new rail and the freshly ground floor with 'weldable primer'. It is new on the market - - and allows you to seal everything before reassembly - and still be able to weld the parts back together.

    Once you have the rail where you think it should be - stop for the day. Odds are high you'll be tired and frustrated - - and just looking to get the damn job done. Better to start with a fresh set of eyes (and patience) the next day! When you restart the second day you'll see little areas that need some more work (although you likely would have overlooked them the previous day).

    Take your time and make sure the rail fits tight to the bottom of the floor. Once it fits well make some scribe marks to help you get the rail back in the same spot (you'll likely have it in and out a couple times).

    A couple approaches to welding the new rail back onto the floor - - I happen to have a 'panel spotter' which works well to create a factory look. You can also get a decent finished product by 'plug welding' the rail too. Usually that is done by drilling or punching holes in the flange of the new rail (about 5/16" is ideal). Most of the factory welds are about 2 1/2" apart - try to do the same when drilling/punching the holes.

    After you have all the holes complete on the flange, you can position the rail onto the floor (remember those scribe marks?), and put a couple light tack welds at either end of the rail to hold it while you measure the distance between the rails. (MIG welders are best for this work) This is when the diagram and measurements from earier will be really handy!

    When you are happy that the rail is in the right spot, weld the rail to the floor by filling up the holes you drilled in the rails. It is best to use a jack or porta-power to put a little pressure on the rail as you begin to weld. The objective with putting pressure on the rail is to close the gap between the rail and the floor - - and to 'preload' the rail a bit. I'd suggest alternating the locations of the welding from front to rear, side to side - - as opposed to welding all the holes on one side of the rail in a row. This helps keep the distortion to a minimum. I usually use a .023 wire on the welder, with a little extra amperage to get good penetration into the floor. The thicker wire will fill the holes faster - - but penetration is the key to having a rigid car when you are finished.

    If you are lucky enough to have a friend helping with the project you might want them to be handy with a hammer and dolly to help 'peen' the welds as you move from hole to hole. If you put the dolly on one side and hammer the weld flat from the other side of the panel it will help knock down the welded area (it will tend to mushroom away from the heat source as you weld).

    Once all the welding is complete clean up all the flash and burn spots with a sander or grinder with a medium grit. If you want a real good job you can prime the bare bare spots with epozy primer, then spary the area with a quick coat of high solids primer. A little sanding with #400 paper (dry is fine), and little wipe with degreaser, a shot of paint to match the interior of the trunk... and you are ready for reassembly.

    Some parts that are nice to have on hand when you start the project include:

    A set of shackles, bushings J-bolts, a new set of leaf springs, and the associate hardware. Odds are high that if the frame is rusted the hardware will break when you try to take the suspension apart. It is pretty common for the main leaf to be broken, and you won't find out until you pry the leaf spring off the spring perch.

    The old hardware that holds the rearend, and springs will be pretty crusty. There is a good chance that they will either break when you try to take them apart - - or of course if you favor the 'blue wrench' you can bet that the hardware and bushings will be toast!

    If you opt to have the work done by a shop I'd guestimate it will cost about $600-$800 per side. About 1/3 of that cost will be parts - the other 2/3 are labor and eyewash :)

    Good luck!

    [This message has been edited by Dave Semko (edited September 17, 2004).]
     
  3. bowtie_70

    bowtie_70 Veteran Member

    Messages:
    683
    Likes Received:
    0
    Joined:
    Mar 24, 1999
    Location:
    Jacksonville, MD
    You can take it to a good welder and he can fabricate new rails for you. I had this done to mine and it turned out really good. It was about 15 years ago, cost 125/side and has held up well. Someone on this board even has templates.
    Definately worth it!

    ------------------
    '70 original owner, factory order, mostly original
    307 (hey, I was a poor college student)
    TH350
    F41 Susp
     
  4. Tallguy2o0o

    Tallguy2o0o Veteran Member

    Messages:
    429
    Likes Received:
    0
    Joined:
    May 25, 2002
    Location:
    Poughquag, NY, USA
    Thanx guys, i found new frame rails on classic industries for $170, and i found out a friend of mine owns a body shop ( i never knew) and he said he'll take a look at it and see what he can do...dave thanx for all the advise, he's gonna let me hepkl him do it, so ill get the knowledge. You guys on this site are a huge helps, thanx again
     

Share This Page

  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.