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1969 Chevy Camaro - Auto Body Repair - Tech
Replacing A Camaro's Rotting Midsection With A Goodmark One-Piece Floorpan
Nov 1, 2007
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1969 Chevy Camaro - Auto Body Repair - Tech
This gaping hole is only the most obvious symptom that body rot, aka "cancer," has taken hold in this first-gen Camaro's floorpan. Note the surrounding metal, which looks like Swiss cheese and is probably about as strong-a potentially serious problem in a unibody car.
This '68 had an undercoating applied at some point in its life, probably by the dealer that originally sold it some 40 years ago. Despite this attempt at extra protection, rust has had its way with the bottom of this Camaro.
The area of the floorpan located directly above the rear torque box is reinforced by an extra layer of steel. As you can see, however, one layer has been virtually eaten away by the elements, weakening a highly stressed area of this Camaro.
Our subject '68 Camaro was stripped down to a rolling shell for its trip to rehab at C. Hopkins Rod & Custom, then media-blasted. Before the rotting factory floorpan can be excised, the front subframe, as well as the rearend and leaf springs, must be removed.
It's critical that body alignment be checked, corrected if necessary, then maintained while cutting out and replacing a major structural component such as floorpan. Proper alignment is ensured by mounting the body shell on a jig built according to the original factory underbody datum line. The body is located on the jig via the master pin holes. "It eliminates the guesswork, aligning the car back to GM specs every time," says Hopkins.
Up front, the body shell is aligned on the jig and bolted into place using the original subframe mounting bolts.
At the rear, locating dowels on the jig are rotated up and into the other pair of master pin holes, found in the rear framerails.
With the body shell securely in place and held in proper alignment, Hopkins began cutting out the original floorpan with a plasma cutter, starting from the center of the transmission tunnel. Note that he cut clear of the spot-welded overlap area at the front of the footwell; this area was dealt with later.
Before cutting alongside the inner rocker panels, it's important to scrape out as much seam sealer as possible. This substance impedes the plasma cutter's progress, and may even ignite. Here, Hopkins has cut a section of the front seat platform away from the inner rocker panel to get at the floorpan. Again, note that he is cutting clear of the spot-welded overlap area.
Once past the front seat platforms, Hopkins switched to an air chisel, which does a better job of cutting through the thicker seam sealer found in this area. With the air chisel, he can also cut through the spot welds, removing this section of the floorpan from the inner rocker panels.
Remember, the rear section of the floorpan consists of two layers of metal, with the rear torque box residing just below. Using an air chisel rather than a plasma cutter allows Hopkins to avoid damaging the framerails by removing the top layer of metal only.
After working his way across the back of our subject Camaro with the air chisel, Hopkins resumed his work with the plasma cutter, slicing up the center of the transmission tunnel and back to his starting point. With this section of the floorpan out of the way, he repeated the process on the driver side.
With the driver-side floor removed, Hopkins was able to stand inside the Camaro body shell and go to work on the rear section of the floorpan. Using the plasma cutter, he cut most of the floor away, but left the sections covering the rear framerails and torque box intact.
At this point, the air chisel was again the tool of choice. Hopkins worked carefully here, peeling back the top layer of metal.
Once the top layer of the Camaro's original floorpan was removed from the torque box area, Hopkins ground down the spot welds that attached the second layer of metal to the framerail. Being careful not to damage the rails themselves, this underlying metal was then pried free.
The idea is to end up with a fully exposed and undamaged framerail, and that's exactly what we got. All that remained here was to grind off the remainder of the factory spot welds.
Hopkins then turned his attention to the inner rocker panels. Using an air chisel, he carefully peeled away the spot-welded remnants of the '68's original floorpan.
The original floor sheetmetal was history, but a host of spot welds remained. Each one was ground flat before the new metal was installed.
Once our subject was totally floorless, Hopkins went over the inner rocker panels with a hammer and dolly, ensuring these surfaces were straight.
The Camaro's skeletal chassis shell was checked for alignment before the new metal was installed. Here, the crew is checking to make sure the rocker panels line up side-to-side; they were also checked with a level for front-to-back alignment.
Speaking of new metal, Goodmark's one-piece stamped-steel replacement floor for Camaros comes complete with the factory center brace found on all cars, as well as the rear brace found on convertibles-a structural bonus for coupes, so to speak. The biggest benefit, however, is the fact this single-piece design replicates the factory construction-and matches its strength.
Setting the floor in place within the Camaro body shell was a three-man job. Once in place, Hopkins had to do some minor pushing and pulling to get the fit just right, but in short order we were ready to make this fix permanent.
With the floorpan securely clamped to the rocker panels, Hopkins spot-welded the new piece into place. Spot welding is cost-effective, maintains a factory appearance, and is plenty strong for this application.
The tabs found on either end of the floor braces, on the other hand, are MIG-welded to the inner rocker panel.
These extra-long clamps were used to secure the front section of the new floorpan to the bottom edge of the firewall for welding. Hopkins uses a single-sided spot welder in this area. The rear of the floorpan is attached in a similar manner.
The final step is to weld in a new set of seat platforms. They do more than just support a set of buckets; according to Hopkins, they tie the floorpan braces and rocker panels together on each side of the car. This entire exercise has been about structural integrity, and these pieces help provide it.
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