Rust Removal - Battling Rust

The floors in this subject Chevy were pretty shot. Most of the rot was concentrated in the lowest parts of the front and rear driver-side floorpans, suggesting a possible leak at the left side of the cowl or perhaps the windshield seal. In this instance, I used patch panels from Danchuk, a company known for Tri-Five Chevrolet restoration parts. Since the rust in this case was extensive, I decided to use the panels in their entirety rather than trimming them down as I sometime do. Now, removal of the old floor (or the installation of new panels, for that matter) doesn't require fancy tools. I used a 4-inch electric grinder equipped with a 4-inch cutoff wheel to cut out the old metal, but anything from a saw to tin snips would work as well.

I started out by laying the Danchuk replacement panel on top of the front floorpan and tracing out the edges using a permanent marker; this gave me a perimeter outline to follow so I didn't cut a hole bigger than the patch panel (I sometimes get carried away). With the perimeter marked, I then hit the rusty floor with a pretty aggressive wire brush to clean it up as much as possible. Then, before I started cutting, I eyeballed the floor really closely, looking for the telltale circular indentations of factory spot welds. Most times, these spot welds are signs of the attachment points of underfloor supports-things we don't want to cut into unless they too are rot damaged. At the front section (about where one's heals would sit), I spied two parallel lines of spot welds indicating a floor support hidden under the floorpan. I used the marker to highlight them and proceeded to finish my inspection and then commence cutting. I then cut out a good-sized section of rotten floor, making sure it was noticeably smaller than the outlines I'd marked out earlier and a good inch away from that line of spot welds I previously mentioned. I then used my much-abused gasket scraper as a chisel to separate the floorpan from the front floor support.

After revealing the floor support, I went back and opened up the hole to the marks I'd made earlier. You'll notice that not only is the exposed floor support just that, it's also one of the Chevy's body mounts as well.

With the floor opened up to the edges of the replacement panel dimensions, I then set the new panel in place and checked the fit. I must have gotten lucky with my cutting because the new panel fit perfectly.

The next step was to attach the new panel to the existing floorpan. Using my butt-weld clamps-which I purchased years ago from the Eastwood Company-to hold the panel in place (you can see a couple of them at the rear edge of the panel in this image), I then tacked the panel in place every few inches around the perimeter.

I had marked and drilled some holes toward the front of the replacement panel that allowed me to rosette-weld the panel to the floor support/ body mount just like the original spot welds had. The indentation and hole you see in the lower left of the image is one of the body mount holes.

With the front tacked into place, I then moved to the rear floorpan. The rotten area is readily apparent here just at the bottom of the hammer handle, but I again opted to use the panel in its entirety. I followed the same procedure I did up front, looking for spot welds and underfloor supports, which I did find, by the way.

The rear panel fit as well as the front one did, although the only extra work I encountered was a bit of trimming (if you look closely, you can see the rectangle marked in the lower center of the image) to expose a couple of factory captured nuts used to anchor the front seat rear outer mount.

Next, I opened up the floorpan again, with the first cut well away from the outer perimeter of the new panel. You can see here the captured nuts for the seat mount that I mentioned in the previous caption (at about 7 o'clock). I spied another row of spot welds just to the right of those, indicating another floor support. This time, I marked the spot welds and drilled them out (I was tired of swingin' my hammer).

This image shows the exposed floor support-well, half of it anyway. You'll also notice I trimmed the existing solid floor around those captured nuts I keep talking about; I trimmed the new pan to match as well. By the way, just to orient the image, the top is toward the driveshaft hump and the bottom is toward the rocker panel. You see a portion of the framerail and one of the exhaust pipes and hanger to the right.

With both panels tacked in place, the balance of the installation job basically consists of finish welding the perimeter of both new panels and drilling the rear pan so it can be rosette-welded to the rear floor support as it was on the front one.

The rear panel goes in just like the front, tack welding it every few inches around its perimeter. Like the front panel, the outer edge of the replacement panel (toward the door opening) is formed with a flange that is attached to the pinch weld of the car's inner rocker panel.

This view shows a good deal of the front and rear floor areas with the new panels in place. At this point, I have about eight or nine hours in on the job, although I do tend to take a lot of smoke breaks. I figure I spent about three more hours finish welding all the edges-welding short distances and then letting everything cool a bit before continuing to keep warpage to a minimum. I'll revisit this particular vehicle in the near future and show the rust proofing and insulating portion of the job, so keep your eyes open.

Welding Isn't The Only WayIn this day and age, welding isn't the only way to mate nonstructural sheetmetal. For those who want to tackle a chore like panel replacement, there are products like 3M's #8115 Panel Bonding adhesive. Yes, believe it or not, one can now glue nonstructural panels together with the strength of a weld. 8115 Panel Bonding Adhesive offers an amazing amount of impact strength, peel strength, and lap shear strength; in fact, NASCAR and the Big Three automakers use it. This adhesive can be purchased at your local autobody supply jobber. It's a two-part mixture that does require an applicator gun, which mixes the two components as they exit the gun. It's a bit pricy, but a heck of a lot cheaper than a welder (although we think a welder is a must for any serious hobbyist).Good old POP rivets are another attachment option for those who don't have access to a welder. Riveting can be used by leaving enough of an overlap between the existing panel and the replacement. If this is the option you choose, just be sure to use a bead of seam sealer between the two panels to seal the joint and protect it from retaining moisture. Like I always say, where there's a will there's a way.