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Process for Rebuilding the Back Half of a Roadrunner

AGillySuit

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Location
Downers Grove, IL
So I somehow ended up with a somewhat doozy of a car that good friend left to me (69 Roadrunner) and it needs a fair bit of work, mostly in the back half. Floor, roof, front frame rails, torsion bar crossmember, interior, windows, etc. are all intact and in relatively good shape aside from a lengthy date with flap disc where there's surface rust.

However, the problem is the back half. Quarters are rotted at the bottom, as is the trunk floor, etc. Rear frame rails are swiss cheesed behind the tires all the way back but the leaf spring perches are still holding, for now. Most people might just say dump it and find a clean one, but it has sentimental value so I'll be giving it my full attention.

Question is, where do I even start with this? The rear portion of the rear frame rails need to be replaced, trunk floor, quarters but I have no idea what order to tackle these in. I feel like if I try and remove the rotted trunk floor and frame rails then the car might lose structure and start twisting. Maybe weld in some support rods to keep the rest of the body in shape? Or will it be fine if I cut out the rear portions of the frame rails and weld in the new ones I have on hand along with the trunk floor before I do the quarters?

I have a bunch of new sheet metal for it and I'm willing to put in the time and work, just have no idea what the order of operations should be.

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That is a ton of work. I would probably go out and buy a few of those spot weld cutters and go to work on the trunk pan. Then work my way around. There are some guys in here that have worked on worse cars and brought them back. Hopefully someone will chime in and give you some direction.

I had a project that was just too far gone ended up using it as a parts car.
 
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Make up bracing and jigs to hold the location of the frame rails, 'cause it looks like you need one or two. Set the car level and make some measurements BEFORE you cut anything. You have to fix the frame first. What do the front rails, crossmember look like?
 
Make up bracing and jigs to hold the location of the frame rails, 'cause it looks like you need one or two. Set the car level and make some measurements BEFORE you cut anything. You have to fix the frame first. What do the front rails, crossmember look like?
The front part of this car is in much better shape than the back. It’s as if someone parked this car with the back half exposed to the elements for decades with the front warm and dry.

Front rails and crossmember are solid, as is the floor pans, rockers, roof, etc.
 
Question is, where do I even start with this? The rear portion of the rear frame rails need to be replaced, trunk floor, quarters but I have no idea what order to tackle these in. I feel like if I try and remove the rotted trunk floor and frame rails then the car might lose structure and start twisting. Maybe weld in some support rods to keep the rest of the body in shape? Or will it be fine if I cut out the rear portions of the frame rails and weld in the new ones I have on hand along with the trunk floor before I do the quarters?


If the back end is this bad, I can only imagine that the rest of the car is just as bad. Being that it's a money pit, personally, I'd question if that project is worth it.
 
Now, now.
It's not always about money with everyone.
And not always a "cover" version, Cyndi.


One of the most important things is to have the deck lid on when fitting the quarters and dutchman.
Getting the gaps and heights on those body gaps as close as you can.
Lots of compromises between them.
And those show.
They hit you in the face.
Don't attach the ductchman aft to the stringers till you get that one "right".
Ask me how I know.
 
Mine started worse....you can do it. I don't do my own frame work, but for my 2-cents, I think Demonic is exactly correct. I've not done this, only watched. You do have to deal with the rear frame rails first. If you are SURE you handle it (out of my league), then setting up a jig to hold the good part of the frame steady & measuring the crap out of everything you can think off + getting ahold of a factory frame dimension diagram makes complete sense to me. Welding in some support rods too, like you mention, make sense. You have the right idea. Starting by cutting out the trunk floor makes sense as well since it's welded to everything. I believe you need to take off the rear end/leaf springs, so keeping that square is obviously important. You've probably figured that part out already
 
Hi Neighbor, Welcome to Da Forum! I'd like to come and look at it and see if you're in over your head?
Maybe let the Pro's do the frame and panel replacement that have the jigs already? I know that we all
want to do this ourselves, but sometimes that's not the best way to go.
 
There is a Satellite near me that has been on craigslist for a long time. Its pretty much gutted however,the frame rails and the actual unibody look to be in decent shape. It does need all of the floor pans but if you don't have to do the frame rails it may save a ton of work. I'll post a link to the car. It may be worth having it as a back up plan. This is a post car so it may not be what you have but certainly useable. Pretty sure the guy would take less. Hell its been on craigslist for I know well over 2 years.

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My 70 Roached Runner is pretty rough also. It was an old parts car left for dead. The good thing is my rails are good. Floor pan and trunk pan are wasted. I replaced the entire floor, slapped it together with parts that I had laying around and is now a super sleeper.

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