I needed a large patch on the passenger side, but a much smaller patch on the driver side. It was also much simpler - no curvature, so I could fabricate it out of raw sheet easily.
I made a cardboard templete, fit it to the car, trimmed as necessary, and used it to lay out the patch on sheetmetal. I cut out the patch with a cutoff tool in an angle grinder, used a bench vice to fold the flanges down, and a flanger to put an offset flange on the vertical and forward edges.
I drilled some 1/4" holes for plug welds on the offset flange.
I cut the bad metal out of the car, leaving room for the flanges to overlap, clamped the new part in good, then welded it in hot, starting with the plug welds, then seam welded all the way around the periphery. I finished up by welding the gap in the flanges.
After some grinding, I've got a solid transmission tunnel once again, ready for the floors.
With the body flipped on it's side, I took a heat gun, a 1" putty knife, a spray bottle of lacquer thinner, and some 3M pads (rough ones) and stripped off all of the undercoat.
This car had a tar-based coating on everything under the body. The only places where it was gone were where it had burned off from proximity to the exhaust. Everywhere else it was hanging on solidly.
This is a fairly satisfying job, a brainless kind of activity. Takes a little time, but only because there's so much to do - you move along pretty steadily, and can quickly see progress.
Step 1 - apply the heat, and scrape off the thick stuff. I wore my welding gloves to protect my hands from the heat.
Step 2 - once the thick stuff is off, spray the area with lacquer thinner and scrub - the remnants flow right off. Wipe off with paper towels, go to a new area, and repeat step 1.
After doing everything convenient to reach with the car flipped on the passenger side, I reversed the "rotation jig", flipped the car on the driver's side, and completed the stripping. No need make the job any more awkward than it has to be...
I'll spray the bottoms with PPG epoxy primer (DPLF), then coat that with color around the edges and wherever parts bolt on, and U-POL Raptor bedliner wherever the undercoat was.
'72 cars came with shoulder harness anchors on the tonneau panel. These were problematic - they weren't retractable, and had to be removed/replaced when the top went up/down. The factory only used these for a couple of years, before going to retractable belts mounted on the inner wheel arches.
Earlier in the bodywork I had welded up and glassed over the tonneau mounting points. Now it was time to install the wheel arch mounting points.
These are BMH heritage parts, sourced from Moss or BV. From inspecting later cars, they are mounted low and back on the wheel arches, about 1 1/4" - 1 5/16" above the rear rail flange (all measurements from inside the car, relative to the center point of the mount) and about the same distance from the rear bulkhead flange. There's a flat mounting boss on the wheel arch just ahead of that location. You might think that was the location for the seat belt mount, but it's not what the factory used.
I put the mount in that location from the inside of the car, marked the outer circumerence, drew several diameter lines across the circle to find the center point, and used a 1 3/8" hole saw to drill the mounting hole. Once I cleaned up the edges with a grinder, it was the perfect size.
From the wheel well, I cleaned off the dirt/undercoat/paint around this circle for a couple of inches.
I prepped the parts by removing all the primer from the weld surfaces, and drilled 4 1/4" holes in the mounting flange for plug welds.
With all the metal bright and shiny, I inserted the mount from the wheel well side, held it in place with a hammer handle, and tack welded it in place.
I plug-welded it at first, then seam welded around the entire periphery of the mounting flange. This was another 'high heat' weld, at the '4' setting. I knew I was hot enough because I blew a couple of holes, and saw good penetration on the inside of the car.
After a bit of grinding and neatening up, task done and one more item checked off the list.
I'm down to 5 welding tasks left - 2 battery bins, one tranny tunnel patch, and 2 floor panels.
My passenger-side heelboard extension had rust holes. The spring hanger underneath it looked fine from what I could see, but with the floor already out, now was the time to replace it, if it was ever going to be replaced.
Getting it off was a job. The surface was so rusted there really wasn't any way to identify the spot welds, so it boiled down to a grinding job. I didn't time it but it seemed like an hour or so.
On portions of the top rear I overdid it, and ground through the rear bulkhead flange that serves as part of the attachment point for the spring hanger - underneath the heelboard extension.
So step 1 was to replace that flange. I cut out a 1/2" wide strip of 18 guage sheet about 3 inches long, drilled it for plug welds, clamped it in place and voila, my ground off flange was restored.
Prepping the heelboard involved test fitting it, and marking the area from underneath that contacts the spring hanger. I then drilled probably 40 or so 1/4" plug weld holes in the spring hanger, and stripped all of the primer off of it where would be welding.
This was a Steelcase part, and the fit was less than perfect. It took some additional forming with clamps, and massaging of the outer flange with pliers, to give me a good fit all around.
I welded this sucker hot, again at 'level 4 of 4', around the entire periphery of the outer and rear edges, and every one of those 40 plug welds. It's not going anywhere...
The best 'before' pic I have - it was marginal to replace it, but now or never...
Old one removed, spring hanger looks good...
Most of the welding done, just the rear edge left...
My PO had seen fit to, well, mutilate the battery shelf panel on this car so that he could fit a particular battery. I assume he did one side, then when the bin on that side rusted out, he did the other. In any event, the 'lips' of both battery bin openings were chopped up, and the battery bin cover no longer could be fastened securely.
No other word for it, than mutilation.
So that had to be fixed. The Roadster Factory actually carries this panel, it's a BMH part, for about $160. A bit steep, when I didn't need all of the panel.
I included this part in my search for patches off a parts car back in 2009. "Dusty from Wagoner" had one, the price was right, and he also had a good sawzall and a long blade. We chopped the panel off, I took it home and set it aside for 2 years.
I gave some thought to only replacing the portions of the rim that had been mutilated, but couldn't figure out a way to guarantee that the bin top mounting holes would all align, so I settled on replacing the entire panel, with both bin openings and all 5 mounting holes as a unit.
While Mike was working on the bodywork, I took the panel off and prepped it, grinding off the remnants of the parts that were attached to it that got chopped off the parts car. The result was a 'pristine' panel, ready to get welded in.
With the car flipped, I cut off the battery bins, then with the car back horizontal, used my patch as a template, marked the cut line I would need to allow for flanges, and cut out the original panel with an angle grinder/cutoff wheel.
Where I had good access, on the sides and partions of the back, I flanged the car, and trimmed everything so that the panel fit on top of the flanges and had a good fit to where I would butt-weld (generally the rear corners and the middle of the back). I drilled 1/4" holes for plug welds at the front edge and the area in the middle a couple of inches back from the front edge where the 'box' in the middle of the car attaches to the panel.
I welded at high heat, I think most of these welds were done at "4" (the highest on my welder). That gave good penetration, minimized the grinding I had to do, and didn't burn through these thick parts, except maybe once or twice in the butt-weld areas.
After grinding, I put on my battery bin cover and marked another item off the to-do list.
I may use some Duraglass to hide my weld seam, but really, it looks pretty good, plenty good for a part that's going to be hiding under carpet.
Over the years, water had soaked the forward portion of the transmission tunnel, under the passenger side heater vents, rotting out the lower flange for about 18". There wasn't anything left to weld the floor to on that side, and there were multiple rust holes above the flange. The PO had slapped a sheet metal patch on the forward/lower section, but hadn't cut any of the rust out, and hadn't cured the root cause - which was that the cowl vent drain was plugged. So the rust just kept going...
"Way back" in the spring of 2009 I had cut some parts off of one of Dusty's cars out in Wagoner, including a chunk of a passenger side tranny tunnel. Now that the car is flipped, and the bottom cleaned, it's time to weld that patch panel in.
First, I had to fix it. The part car panel had rusted too - it's flange was fine, but the area directly under the vents was rusted up pretty good, with several rust perforations. It took 5 patches, some big, some small, to make the part solid again.
Then I cut out all rusted area from my car, flanged my replacement panel, clamped it in, and welded it. I welded the edge of the flanged area, on both sides, at a high-heat level (3 out of 4). I got good penetration - this patch isn't going anywhere.
Once the main patch was in, I had to add another small patch where the donor patch still wasn't quite big enough. Not a big deal, just the standard process - I made a pattern out of light cardboard, holding it up to the hole and marking with with a permanent marker. I then cut out the cardboard pattern, and used it to cut out the patch from raw sheet. I tacked the patch in, formed it a bit with a hammer as necessary, then welded it in all around.
There's a similar issue on the driver's side, but much smaller - I'll just use raw sheet to make a patch for that.
The 'before' shot. The problem had been patched before - somebody had slapped some metal over the rust and called it a day.