replacing front frame rails

[American_Muscle]

I am getting a 1970 superbee that has major front end damage, how hard is it to replace the frame rails, it is a factory 383 car, I have a 318 1970 Coronet that comes with it as a parts car.
Kevin

[Rolling_Thunder]

It will be a bear to say the least...     I have done my share of fabrication but that scares the shit out of me...     You couldn't pay me enough to screw with frame rails...       then again to someone who knows what they are doing it might be second nature.

[American_Muscle]

well, I feel less inspired now, lol. I was planning to do the full resto myself... I'll have to look it over and definately measure, weld and double check everything

[Blown70]

well, I feel less inspired now, lol. I was planning to do the full resto myself... I'll have to look it over and definately measure, weld and double check everything

MEASURE MEAURE MEASURE, then measure some more.....It can be done but wow, yes, did I mention measure.....

Some will do a rail at a time, and not take both out at once maybe an option too?

[American_Muscle]

Replacing one at a time might well be the best idea I've heard so far, at least it then gives a point of reference close by. I'll keep you guys up to date as I get underway. Just hoping the car doesn't have a totalled title.... I need to talk to the guy
Kevin

[RallyeMike]

It's hard to say what is the best plan without seeing the car, but.....  If I was doing this and had a complete donor car, and the Bee is really that heavily damaged, I wouldnt mess around with little bits of work. You could be screwing around grafting things and straightening things here and there and never get it just right.  I'd chop the clip off including the inner fender wells and graft on the donor car replacement trying to use most of the factory weld points. If the car is that badly wrecked to bend both frame rails, the fenderwell sheet metal is going to be a mess too. The bonus to this plan is that you are more likely to get the overall alignment correct and not have to worry about tweaks and twists that you don't see. The gut check part is deciding if you chop off and weld in the the new frame rails at the firewall or try and replace the whole shebang back to the rear crossmember (a lot of extra work).

Look the whole car over carefully before you get started. You might find warps and split seems in the floor pans, or who knows what. If there are a lot of other body tweaks from a very heavy collision you might want to think twice about it or plan on having the car placed on a frame rack when you are done.

[Mike DC]

Here's what I'd do:

1.  First get the unibody to a frame shop and have it professionally pulled back to factory specs.

2.  Then drill out the spotwelds & replace the subframe rails that had been badly kinked in the wreck. 



This way you're hitting the ground with a basically straight set of unibody sheetmetal aside from the rails.

If both front subframe rails have to go, then I would probably see about getting them in a one-piece "clip" attached to the tranny crossmember.  Swap that whole chunk in one fell swoop. 

[American_Muscle]

I'll have to look around for a frame shop near me, Hard to find much around here in terms of serious auto body, but I'll look
Kevin

[Mike DC]

It's worth a search.


Depending on how & what is bent from the wreck, you might get away with just swapping on a set of straight rails and yanking the sheetmetal as necessary by hand when you weld it back together.  But I'm just saying it's a risk to cut those old rails off without having straightened the unibody already.  A frame shop really needs the old rails still on the car in order to do the job right, both as a reference point and as a viable place to attach pulling points onto. 




Either way, don't be afraid to do this kind of work if the rest of the car seems worth it. 

I know this kind of serious collision work makes people cringe and say "man, find another body."  But the truth is there's nothing too smart about rebuilding a straight body if it means re-skinning & re-flooring 2/3rds of the whole structure with Chinese replacement metal either.  That kind of gigantic rust repair has just become more socially-acceptable in the hobby these days for some reason. 

[lilwendal]

Depending on the extent of your structural damage.  No rocker or firewall damage...
What Ive done is remove both frame rails, torsion bar mount and front radiator support as an assemble from a donor car.  Drilling the spots where they come from the rear cowl to the inner fenders will release it from the body there. Drilling the spots from the floor pan to the torsion mounts and aft front frame rails.  Then drilling the torsion mount free from the rockers.  Comes out as a complete  boxed assembly, retains all factor dimensions, and requires minimal welding to reassemble. The radiator upper and lower supports hold it all together up front and the torsion mount holds it together in the rear.  You can also leave the K member installed for added strength to the structure and also permits a center point for lifting and adjusting when reinstalling.
Like mentioned before..The car has to be correctly shored then measurements taken to asure your donor assembly gets into the correct position.
There are many factory aids that make the job easier like cut outs and allignment punches in the metal that almost make it fool proof.
No job for the amatuer welder.  You have to be confident your welds are as strong or stronger the when you removed.
I've done this twice before and it works beautifully and can be accomplished in about 3 or 4 days with proper tooling.