Left Front Outer Frame Rail Patch

I took the day off from work today to celebrate my birthday (thanks Dave!), and felt the need to try my hand at frame rail repair. You see, when I was disassembling the car to take to the shop, I removed the left front bumper bracket from the frame rail. The bumper bracket was rusted out and had left some rust scale behind on the frame rail so I pulled out my trusty air chisel to clean it up and clean it up I did! The center of the frame rail between the mounting nuts, popped off in in hand to the tune of various expletives. The Mustang shop guy told me that this was normal damage... for the passenger side under the battery tray due to the corrosives that come from the battery but he'd never heard of this happening to the driver's side. Weeeelll, paint me pink and call me Shirley, ain't I lucky!? Here's how I decided to tackle the problem:

This is what we started with. Looks scary, better total out the car right!?
Bah! I have a 4.5" angle grinder and I'm not afraid to use it! First we gotta clean up the area to ensure the rust stops at some point. I chose a line in front of cross member that attches to the bottom of the rail and between two spot welds top and bottom and cut the slot. I used my sawz-all to finish the cut on the bottom flange. Also, at this time, I noted the location of the captive nuts on the area above the frame rail so I could ensure that the horizontal alignment of the holes of the new part are identical to the old.

I drilled out all of the spot welds and popped the old outer rail off with the air chisel. Now, the repro frame rail I bought to patch this has captive nuts welded to the rail itself so you have to imagine my surprise to see this bracket welded into the frame. I certainly was not expecting this. I thought the captive nuts were welded to the outer rail like the repro rail. I determined that this bracket was partially responsible for the deterioration of the rail since it left lots of places for water to get in between and no way to drain or evaporate.

4 spot welds were holding it in so I cut those welds and air-chiseled it out. I considered briefly to fab a new bracket but decided against it because I don't have any better way to seal the bracket to protect it from moisture (other than paint) than Ford did in 1968. Plus I'm not setup to fabricate sheet metal parts with tight bends out of metal as thick as 14 gauge. I ground the inside of the rail as much as I could reach with my tools and then treated it with Jasco Prep & Prime, and then sprayed primer on as much interior rail as I could get to and finally, treated the weld surfaces with weldable primer.

This is the repro frame rail patch with the old rusted parts. I cut out the new patch by measuring against the hole locations I took in the above step and the vertical cut from the car where the old rail was cut out.

Here is the preliminary fitting of the new patch. I've predrilled all of the plug weld holes and have adjusted the angle of the upper flange using the precision "smack it with a hammer till it fits" methodology. Also, the front edge of the patch had to be straightened flat to mate with the front frame rail.

I used clamps on the bottom flange and sheet metal screws on the upper flange to draw the outer rail patch to the inner rail and made tack welds all along the patch until it was tight (along with some strategically placed hammer blows). Finally, I finished the plug welds and welded the patch to the existing outer frame. My new birthday present really helped a lot on this step.

The welds were ground down flush...

...And then primered for that not-so-rusted look. Note the old, rusty, frame laying dejected on the ground never to see the road again.