Removing the old, Rusty metal — Passenger Side

Passenger torque box rear

Before I cut any material out of the car, I leveled the chassis, and put jack stands under the frame rails.  I also installed a cross brace between the mounting points for the top. I then checked the measurements against Ford’s frame alignment spec (See first picture).   To double check I also measured the distance from the trunk hing mounting bracket to the top of the windshield on both sides.  All the dimensions were good.  so we know the car is straight, and in good shape.  Also the car does not show any signs of collision damage.

After inspecting the car, I determined that the passenger side was in worse shape than the drivers.  You should always start with the weakest side.  The reason is that the stronger side will hold more stress, and so you need rely on it to hold while you fix the weaker part.  This way once you have repaired the one side, you are still moving to the weaker side (Since the repaired side is now up to original strength).

Next I welded 2 braces running from the cross brace to the windshield frame, one on each side of the windshield.  If you read a lot of the web forms there seems to be some debate about if the additional bracing is necessary or not.  The argument against goes something like this:

“The car’s unibody, and chassis are designed to carry the car (Engine, all body panels, drive train, …) fully loaded over bumps and rough roads.  Given this if you remove all the weight except the chassis, it is more than strong enough to hold itself when you remove the floor, and other parts.”

There are two parts of this I disagree with.  One when you start working on a car you don’t always know how much you are going to have to remove, so any extra bracing will help when you cut more than you originally planned.  Secondly it is easy to fabricate and cheap to build, so better safe than sorry.

The pictures labeled passenger torque box in this set show its condition.  The torque box is designed to connect the front frame rails to the side frame rails.  Not all Mustang coupes and fastbacks before 69 had torque boxes on both sides.  Convertibles always had both torque boxes.  This was necessary since there was no roof to add additional chassis stiffness.   From the photos you can see that this torque box is not in good shape, I have highlighted some of the rust holes.  I then cut an inspection hole in the front part of the torque box, you can see that it is no longer attached to the frame rail on the front.  After drilling out what seemed like 50 spot welds and using the air chisel to remove the parts I have the torque box removed.  This job is a lot easier if you are not trying to save the lower part of the firewall.  I’m trying to keep as much original metal as I can, so I had to remove the torque box in several sections.

With the torque box removed, I went back inside the car, and removed the seat pan.  As you can see the floor is quite rusty underneath.  Convertibles have two seat pans, a upper one, that sits inside the car, and a lower one underneath the car.  The floor pan is sandwiched between the two.  Typical of cars in the 60-70s the metal was left unprotected, and being in a captive area moisture and dirt just sat there and rotted out the parts.  Also in this photo, you can see one of my favorite tools the plasma cutter (an electric cutting torch).  Plasma Cutters do the same job as an oxy-acetylene cutting torch, but you don’t need the gas.  Just an air compressor, and electricity.

Using the Plasma cutter I cut the lower seat pan off, and then cut out the floor pan.  I stopped short of the frame rails.  I then marked the spot welds on the frame rails, and drilled them out using a spot weld cutter, or a rotabroach cutter and WD40 for lubricant to keep the cutter cool and ease cutting the hardened welds.  once the spot welds were cut out I used a die cutter to carefully cut through the floor but not the frame rail.

Next I started to assess how much of the frame rail I could salvage.  I started by cutting the inner frame rail out to inspect how much rust there was.  You can see that the inner frame rail is rusted through in several spots.  The good news is that the main frame brace is in pretty good shape.  I only had to cut out about 12 inches near the rear fender as shown in the photo.  With the section cut out, you can see that the rocker is in good shape, and the galvanizing that Ford put on about 40 years ago is still holding up.

Next time, we patch the frame rail and start treating the rust.