55 car rust repair Part 1: Floor

[Daves55Sedan]

The rusted out right front floorpan was cutout as pictured below mainly with a jigsaw. I used a cutoff wheel in a drill to pass over the floorbraces without cutting in to them. I used first a drill, then a Dremel tool to grind out the resistance welds that held the floorpan to the floorbrace. Then I removed the body-to-frame bolts and lifted the rusted floorpan out and discarded it. Note: if you select a photo to view it enlarged, there may be some additional text on the photo giving identification or description (typical throughout).
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A sheet of cardboard was used to make a template by placing the cardboard over the hole and pressing my thumb all around the cutout. Then the cardboard was cutout at those markings and placed over a flat sheet of 18gage sheetmetal. I used an ink pen to mark the metal around the edges of the cardboard. Then I cut out the sheet with a jigsaw. I made several little sheetmetal tabs from scraps and fastened them under the floor at the cutout so that the new panel would lay flat on top of them and the panel would be flush with the existing floor. I used a punch to punch my holes for the temporary sheetmetal screws and bolted the floor in place. Next was to mark the locations where the body-to-frame mounting recesses would be. I got underneath the car again with a sharp metal scribe and poked it thru the mounting holes and scratched a centerline at each hole location. Next the floorpan had to be removed AGAIN. Turning the floorpan over so its backside was facing up revealing my centerline marks, I used a centerpunch to mark the center of the holes. I found two large washers that would fit down inside the floorbrace, also having a large enough hole for the bolt to go through while at the same time be large enough to accept the floorbolt washer. Luckily I had several in my stock of washers. I used the outer diameter of the washer to mark the cutout on the floorpanel. I started by using a drillbit at the centerpunch mark, then inserted a jigsaw blade thru the drilled hole to finish cutting out the large hole. Next I measured the depth of the recess at the floorbrace. Using more scrap metal, I cut a flat strip whose width would be less than or equal to the depth of the recess. I wrapped the flat strip of metal around the washer and cut it where the two ends met so that it would make a cylinder to fit tight around the washer. Then I clamped the pieces together and welded the washer to the cylinder. Next was to weld the new recess to the hole in the floorpan. Laying the pan upside down on the garage floor, I simply inserted the recess upside down so that the cylinder fit snugly into the hole, then welded the recess to the bottom of the floorpan. Repeat procedure for the next mounting bolt. Considerable grinding with a dremel tool at the backside of the floorpan at the welds was required due to the tight fit of the recesses into the floorbraces but it did work out beautifully. Now I again temporarily re-installed the floorpan with the body to frame mounting bolts and the sheetmetal screws. Tightening down the bolts caused the panel to conform to the "swale" in the floor (which is what I wanted). I got underneath the car and marked the bottom of the new pan representing the location of the edges of the floorbrace using an ink pen. Then I removed the floorpan and drilled holes for sheetmetal screws at locations that would be in the middle of the floorbrace flanges. At this point, I primered the underside of the new panel and applied enamel overcoat to the underside. Then I re-mounted the floorpan and drilled thru the floorbrace flanges at those hole locations and added more sheetmetal screws there. Later, all the sheetmetal screws will be removed and I will weld the new panel to the brace and the tabs at those holes filling in the hole after welding the panel in place all around the cutout.
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I did not attempt to duplicate the floor stiffener bends that were in the original floorpan, since this was on the passenger side (where there is never any feet to rest upon it anyway), and this is 18gage and pretty rigid once fitted and welded in place.
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The driver side front & rear floorpans and the passenger side rear floorpans that I had replaced in 1992 had stood the test of time, but the paint became corrupted by water soaked jute floor backing all those years. Each panel had large areas that had heavily rusted, but luckily there was no pitting of the metal. I used medium grade sandpaper for starters, then ended up polishing down with a waterproof fine grade self-stick sanding disc attached to a drill. Just cleaning up the floor to get ready for spot primer took half a day. Masking off all the windlace and papering over the dashboard/firewall was a long and arduous task as well. Finally, the overcoat was applied to the whole floor with a cheapo Harbor Freight detail spray gun.
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[frank long island]

I remember doing my wagon the only difference was I used a ball peen hammer for recess's I also put a peel and stick sound deadener down after I primed

[Daves55Sedan]

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Originally Posted by frank long island

I remember doing my wagon the only difference was I used a ball peen hammer for recess's I also put a peel and stick sound deadener down after I primed

I considered using a large socket (1-1/2") under the hole location as a template with a smaller socket above to be hammered down on the floor panel at the hole location, but it would have required extensive heating to stretch the metal and I was concerned about distorting the metal that I wanted to remain flat, so I chose not to hammer down the recesses. Also it would have been very difficult to get the large socket underneath centered in the hole. The way I did it, I got the location exactly where I wanted, got the depth I wanted and got the rigidity that I wanted. It was just a lot of work to get it.
After the primer and base enamel overcoat on the finished floor, I cut out roofing tarpaper and laid it down over the floorpans, transmission hump and footrests. (2) pcs; one for front floor and one for rear floor. Then, I salvaged some of the jute backing on the old rubber floorcovering that was still good and replaced the bad portions. I agree that a sound deadener would be much better, but I had a roll of tarpaper from a previous roofing project and also had a roll of jute laying around, so I used them without spending any more money. I was never concerned much with noise, the main purpose for the project was rust removal and prevention.