Sunday, February 20, 2011

Floor removal, toe board eval & frame rail straightening

Now that my taxes are filed and I'm square with the Fed for one more year, I was able to get back to business on the Boss.  With the cowl complete, the next step was to begin the process of repairing the floor area and all of the associated areas that required attention.  There is nothing “pretty” about this phase of work and the pictures certainly reflect this, but with this ground work in place, the end results will ultimately show the effort.
I decided to tackle the removal of the floor pan by first removing the seat pans.  As previous pictures will show, the floor in my car was a mess, with little salvageable material left to use.  As such, I didn’t need to be especially frugal in the removal of the bulk of the floor pan structure, so out came the smoke wrench (a.k.a. oxy/acetylene torch) and after a few minutes, the seat pans were history.
With more room to work, I could now concentrate on getting the floor pan out of the car.  Here again, there was nothing left to save, so I decided to employ my trusty recip saw for the removal of the majority of the old floor pan.  I decided I would take the floor out in three pieces beginning with the center and leaving the front and rear sections for later.  Mainly, I did it this way to make it easy, but also to allow a more precise removal of the front and rear sections where considerable spot weld cutting would be required.
Once the center section was out of the car, I concentrated on removing the front section attached to the front frame rails, the transmission tunnel brace and front toe boards.  There were a lot of spot welds involved here and I was once again thankful for the efficiency of my Blair spot weld cutter.  After a few hours of work, I was able to carefully peel the front floor section away and have my first serious look at the frame rails and toe boards.
As I have mentioned on numerous occasions in the past, the abuse this old car has taken in its life is hard to imagine.  Almost everywhere I look are signs of an extremely hard life and the lower surfaces of the frame rails were certainly no exception.  First off, Mustangs were never designed to tolerate jacking on the frame rails.  As a unibody car, they were designed to be jacked up along the pinch seam that runs along the bottom edge of the rocker boxes.  This is the area where the car is especially strong and capable of supporting the weight of the car without damage to the structure.  Somewhere along the line, someone was very enthusiastic with a bottle jack of some kind, and had managed to severely damage the bottom of both frame rails with deep, quarter-sized dents the exact shape of a bottle jack pad (ugh!).
I spent several weeks pondering the most effective way to repair these areas, particularly since the frame rails were in such good shape otherwise and had miraculously managed to avoid the heavy rust damage the remainder of the floor had endured.  In the end, I decided to basically use the old hammer-and-dolly technique, expect the dolly was going to be a piece of flat steel plate on the end of my frame jack post pad and the hammer was going to be a combination of 2-lb sledges and a simple forming tool I made from some spare ½” plate.  I knew ahead of time I wouldn’t be able to remove the deep scars from the bottle jack pad, but I felt I could get the frame rails straight enough that a thin skim of filler would be all that was required to make them perfect again.  I am happy to say the results were even better than I expected.
With the frame rails in good shape, I turned my attention toward a comprehensive evaluation of the toe boards.  I knew I would need to replace the obviously rusted lower edges of the toe boards, but wasn’t sure how far up the firewall I would need to go to get back to good metal.  As it turns out, the repair of the passenger side would be quite minimal in scope and the driver side would be quite manageable as well.  I wanted to keep the amount of weld seams inside of the trans tunnel to a minimum such that the metal finishing would be minimum and the least amount of filler would be required to make these repairs invisible.  Looks like I just might get my wish!
Next up, I will start preparing the toe board repairs and tidying up the frame rail and transmission tunnel brace flanges.  I will also remove the remaining flanges from the old floor as well as the rear floor section under the back seat area.  Somewhere in there, I hope the weather breaks enough to get some sand blasting done in these areas as well.  That should really make everything not look so much like a junkyard dog…….c’mon SPRING!
A few minutes with a torch and the seat pans were outta there.  This made the rest of the floor removal quite easy.

My recip saw handled the bulk of the floor removal with ease.

I left the front section of floor in place as there were numerous spot welds that required a rather precision approach to removal to ensure minimal damage to the parent structures underneath.

After a few hours with the spot weld cutter, the front floor section was removed without much fuss.  This allowed a much more comprehensive inspection of the inner frame rail surfaces as well as the toe boards.

Here you can get an idea as to the extent of damage there was to the bottom surfaces of both frame rails  from the use of a bottle jack.  With such structurally sound frame rails, I had to figure out how to repair this damage rather than replace the rails.  This is the passenger side"before" shot.

Using the jack posts I made during my cowl replacement, I fashioned a flat steel "dolly" that gave me a hard surface to work against when reshaping the lower frame rail surfaces.  The adjustable jack post on the opposite side of the car was extended to provide slight pressure on this assembly to provide a solid work surface.

While generally ill-advised, I used a small 2 lb sledge as the first means to get the damaged metal moving.

For the finer work, I made a simple bucking die that allowed me to restore the shape of the corners and edges of the frame rails as well as the bottom.

By turning the bucking die sideways, I could rather easily restore the lower frame surfaces by simply walking the die up and down the length of the fixed dolly until the surface was nice and flat.
Here's a rather poor shot of the driver side frame rail during the straightening process.  You can easily see one of the remaining heavy dents just to the left of the trans tunnel brace flange that has yet to be removed.  The jack post and dolly can be seen in position at the far right of the picture.

Here is the driver side frame rail after straightening.  Notice there are no more nasty, jack-induced dents in the lower frame surface!  A small amount of All-Metal filler and these surfaces will be nice and smooth.

Here's the passenger side frame rail after repair.

After careful examination of the exposed rust damage, I marked the passenger side toe board using a bit of soapstone.  Nothing too extreme required here.

Similarly, the driver side toe board repair section is surprisingly minimal given the extent of rust damage that was in most sections of the original floor.


  1. Nice work and attention to detail there Sven!

  2. Thanks Alex! I'm looking forward to some sand blasting time so it actually starts looking like something to brag abvout. This floor is a real mess......

  3. Nice idea with the bucking die. And as always great work and blog!

  4. I appreciate that James! I reasoned that if I could do essentially the same thing with a hammer and dolly to much thinner sheet metal, it might just work on the thicker metal of the frame rail. Worked great!

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