How to Replace Muscle Car Metal
By John Gunnell
Floor Pan Repair
Reproduction Camaro body panels are readily available, but sometimes it's just as easy and cheaper to fix small rust holes in sheet metal. Keep in mind that the actual size of a rust hole is rarely what you see at first. It's what you wind up with after poking and cutting out rusty metal. What starts out as a small opening can become a huge crater. If you have a crater, you'll need new floor panels. These come single-piece (complete floor) or as right- and left-hand panels that run the full length of the floor on each side of the transmission tunnel.
For small holes, cut out bad sections of the old floor and trim replacement panels to fit inside the cut out area. Then butt-welded them in place. Butt-welding eliminates overlapping sheet metal where corrosion could re-start. Use a MIG welder to hold the trimmed panels in place. Put tack welds at all four corners and fill in with tacks every few inches around the perimeter. Once everything is tacked, weld different areas a few inches at a time to keep the pan from heating up and warping. Wear a welding helmet and heavy welding gloves.
If the rotted floor area is not too large, cut out the bad stuff.
Once all the welding is done, the welds underneath the car can be ground smooth. Leave a little weld on the top for extra strength. Then use waterproof fiberglass filler to provide strength. Apply standard filler over the repair for final shaping and forming. Then use epoxy-based Spot Filler putty for final fills. This putty is much thinner than Bondo and fills in sanding scratches and air holes.
After butt welding trimmed section of replacement panel in place, dress the weld and finish off underside of repair with fillers.
Cutting out the bad sections of the old floor can be tricky, so do this carefully and try to get the best tools that make sense for you. An Air Whizzer tool and an air saw with a very small thin blade can be used. An angle grinder and cut-off wheel works, too. Another option is an air-powered chisel if you have a big compressor that won't leave you high and dry on air every few seconds. Ultimate is a plasma cutter. The cover of the latest Eastwood catalog shows a floor being cut open with a plasma cutter that Eastwood sells for a hobbyist-friendly $640. If you do a lot of work on cars, this tool may be worth buying. If you're only doing the one car, perhaps you can borrow one or use other tools.
Windshield Channel Repair
Corrosion in the windshield channel area is common. This is the "lip" that the windshield glass sits against. Cancer occurs due to water seeping behind the 40-50 year old bead of dried-up gap sealer and laying in that area for a long time. Adding to the problem is that late-1960s automobile production processes did not ensure that the metal lip was always well protected by primer or paint. In addition, the factory finishes used back then were not up to lasting a half century. This created a situation where moisture tended to collect where there was bare metal or where finishes wore off. This made the channels very rust prone. The same was true for the rear window channel on closed cars. In both cases, the problem and cure are the same, so rear window rust repair is very similar.
After removing the glass, cut out the corroded spots using the Air Wizzer cutting tool. Take out all the rust until hitting solid metal. Then, use pieces of 90-degree angle sheet metal to cover where the cancer was cut out. Cut notches in the angled strip so that it can be formed to match the contour of the windshield.
Cut out rot in windshield channel.
Weld angle into the area you cut out in the windshield channel.
Once each angle piece is tack welded into position, the perimeter and the notches can be welded up using a MIG welder. Remove any excess weld by using the Air Whizzer and die grinder. Try to keep the repaired area from extending into the roof panel. This way, most of the windshield channel that repairs had been made to will be covered by the bright metal windshield trim.
Clean up the weld with a die grinder or air whizzer.
After tack welding the angled metal patches in place, use waterproof fiberglass filler to add strength and water resistance to the repair. Then apply smoother filler so that the corners of the windshield can be shaped properly. Avoid using lots of filler where the windshield sits to allow a good bond later.
Hide repair with fiberglass filler and smooth filler top coat.
Rear Quarter Panel Repairs
If your Camaro's rear quarter panels are rusty, it can be more work to weld in partial panels than to install full replacement panels. With the smaller sections there is a higher likelihood of future rust and potentially more bodywork issues.
Replacing the quarter panels is a challenge, due to the amount of cutting and fitting and alignment that is required. Try to save the original factory trunk lip. Though it seems amazing that the entire rear of a body can be reconstructed working off this thin lip, it can be a key factor in making sure that the new quarter panels align properly. It's also good practice to replace the rear quarter panels just one side at a time to avoid losing the alignment of the trunk lip.
Amazingly, the rear end was completely rebuilt off this thin trunk lip.
Major quarter panel repair begin by cutting out the old quarter panels with the Air Whizzer tool. Cuts are made along the inside of all connection points so that only an inch or two of material is left at all those spots. Use a spotweld remover drill bit to remove all spot-welds and an air chisel to remove the final inch or two of metal. All of the factory-applied lead filler has to me melted out of the overlap where the rear quarter panels meet the roof. Use a torch and wire brush to remove old lead filler and get the panels to mate as neatly as possible.
The old quarter panels were completely cut away.
Once the area is cleaned of lead, go over it with a wire wheel. This makes the factory spot-welds show, so that they can then be removed. All attachment areas should be cleaned up with a wire wheel and Air Whizzer. They are then covered with "weld-through primer" to prevent future rusting.
The replacement rear quarter panels have to be trimmed to fit. About 20 test fits and re-trims will be done on each side to ensure of a proper fit before the rear quarter panels are welded in place. The panels also have to dovetail with the rear window base panel that runs across the top of the trunk. Then all of these panels have to be re-checked for proper alignment before final welding.
Holes should be drilled in the edges of the replacement rear quarter panels so that you can MIG weld through the holes onto the original metal and keep making small circles inside each hole until it fills and overlaps the new metal. The use of this technique creates a type of weld that looks similar to the original factory spot-welds, once the welding material is ground down.
The area at the top of the rear quarter panels came from the factory with a lower flanged edge that allowed filler to be used after it was welded. To replicate this continuously weld the top of the rear quarter panels, which adds strength too. Weld behind the drip rails and, with minimal bodywork, remove the excess welding material. This gives you an appearance that looks just like the original factory edges. Many restored cars wind up with gobs of silicone or body filler inside the drip rails to hide where the quarter panels were replaced. Instead, weld up this area, then grind down the excess welds and fill in seams with fiberglass filler. Then sand, add plastic filler shaped to the original quarter panel profile, and sand again and again until you get the area looking perfect.
New quarters must be aligned at roof before welding and filler steps.
Before doing metalwork on Camaro doors, replace the door hinge pins so your doors swing tight. The doors should also be taken off and put back on at least a dozen times to get the gaps just right. Then do your final hinge pin adjustments to get perfect door alignments. Then drill 1/8-inch holes through the door hinges so that a drill bit can be used to realign the hinges and door any time the doors are taken off the car. Also do this to your hood and trunk lid hinges so that any of these panels can be removed and reinstalled in the same position.
End results of the first-timer D-I-Y project were very good.
If the doors do not mate well with the replacement quarter panels, the door "margins" will have to be reworked either by welding more material on the edge of each door or grinding off some of the edge to match the door to the profile of the rear quarter panel. This requires welding the ground down edge with a MIG welder, but gives you very durable door edges that match the gaps correctly without using body filler. Otherwise, body filler would have to be formed into the quarter panel to match the door and would likely chip off as the doors were used.
Door edge margins had to be reworked to get proper alignments.