Quarter-Pounder

Posted on May 11, 2015 by Jefferson Bryant in Fabrication, Paint/Body, Projects, Tech // 0 Comments

Inheriting a project from another person sometimes means getting to fix things that had been glazed over. Such is the case with this 1965 Mustang coupe. This particular Mustang is a solid straight-6 driver. The interior is all new, the 200 ci 6-popper runs really strong, backed up by a C4 out of a truck. The only problem the car really has is the paint has seen better days. There are only 2 spots of rust, over each rear wheel well. Patching that is simple enough, but often you find a few hidden demons in that process. As we discovered on the ’65, the car had been hit in the rear passenger side. Instead of a proper fix, most of the damage had been beat out with a hammer, then filled with bondo. That wasn’t going to do.

The bulk of the damage is on the quarter panel itself, so we decided to replace it. There are two ways to replace the quarter panels on an early Mustang—a full skin, or a reduced skin. A full skin is the entire quarter panel section just like the factory stamped. This panel includes all of the factory flanges, complete from the sail panel, trunk opening to the wheel well. Installing one of these requires completely dismantling the car. The other option is a reduced skin, which covers the wheel well up to the top of the body line, door jamb to the tail panel. The advantages of a full skin are very little bondo work, no warping from welding, but they take longer to install and cost several hundred dollars. The reduced skin requires more effort in terms of welding (which means warping), and requires more body filler, but they are much cheaper, and when done correctly, provide the same level of finish.

We opted for the reduced skin, which we sourced from Dallas Mustang. The skin cost $59, which is a stone-cold bargain for the quality piece that we received. Usually the cheaper a panel, the more work it takes to get it to fit. We only had to modify a couple of areas with some wide-mouth pliers to get the perfect fit. There are a few things you need in order to install a quarter skin: Mig welder, cut-off wheel, grinder, drill and spot-weld cutter, body hammer, and a screwdriver. We used a couple of specialty tools that make a big difference in simplifying the job- a punch/flange tool and a set of electric sheet metal sheers. We also discovered some collision/rust damage behind the quarter panel during the repair. We ended up making a patch panel with our Woodward Fab 3-in-1 fabrication machine.

The entire process, from beginning to end can be accomplished in about 2 days if you are experienced, expect a few delays if this is your first time. The key to a quality quarter panel replacement job is patience and fitment. Getting in a hurry will create problems that you may not even realize until much later, and then you have to start all over.

01. At first look, there does not seem to be much damage, just a little rust and some light bondo.

02. One look in the trunk, however, shows a different story. There is a long crease that has been filled with bondo, complete with bondo worms. This had to go.

03.We ordered a new skin from 1-800-Mustang, and it fit quite well, considering its $59 price. We set the panel to the car and marked the top line of the new panel on the car. This will serve as our overall fit line.

03. We ordered a new skin from DallasMustang.com, and it fit quite well, considering its $59 price. We set the panel to the car and marked the top line of the new panel on the car. This will serve as our overall fit line.

04. We measured ¼” out (towards the side of the car) and marked our cut line. This leaves a ¼” overhang, which will be flanged later. You could butt-seam this repair, but that just isn’t necessary.

05. There are quite a few spot welds in the door jamb, wheel well and tail panel on the original quarter panel which have to be cut. To make it easy, we used this spot-weld cutter from Eastwood. The spring-loaded pilot bit makes this much easier than any other spot-weld cutter.

06. The end result looks like this. The weld is cut, leaving the underlying metal intact. There is a spot weld about every 1.5-2 inches.

07. To simplify the removal, we used a body ripper and an air-hammer to separate the lower section of the panel from the body. We cut this about ¼” up from the factory seam.

08. A die-grinder and cut-off wheel was used to make the corner transition where the body-ripper cut to the spot-welded section.

09. Up top, the electric sheers provided a straight cut in about 2 minutes. Doing this with a cut-off wheel would take much longer and would not be as straight.

10. With the skin peeled back, we could see some additional damage. The lower section was rusted out and the back side was smashed. We didn’t have time to order a patch panel and this is a simple flat piece of steel, so we made our own.

11. We made a template from cardboard and then transferred the shape to a piece of 22-gauge sheet metal.

12. Then we cut it out using the 3-in-1 metal machine from Woodward Fab. This machine cuts, bends, and rolls up to 18-gauge steel, it is a godsend for any sheetmetal fabricator.

13. With the new panel cut, it was welded to the Mustang using our MillerMatic 211. The panel just needs a spot weld about every 2-inches.

14. The one major problem with the new panel is the top lip. Due to stamping, the lip does not have the correct angle. We made a template that conformed to the original quarter panel to check this.

15. The angle was easily altered using a set of wide-mouth pliers shown here. With this done, the panel was a perfect match.

16. The bottom edge of the quarter was trimmed to fit into the lower section of the body. Using a punch/flange tool, we added a flange to make the two panels flush. We also flanged the top edge of the original quarter panel that remains on the car.

17. With the panel in place, the door jamb gap was excellent, but the panel was sitting in a bit too far. Forget to check this and your door alignment will never be right.

18. We adjusted the panel and set it with a few sheet metal screws. Before mounting the panel, we punched some holes for the spot welds.

19. Shipping and several rounds of test fitting can bend things a little. A few well-placed taps with a hammer get things right again.

20. Then we spot-welded it in place. You want to work from one end to the other, so that you can work out the kinks along the way. Always start at the door, working backwards, welding up the tail panel last. That is where you have the most adjustment room.

21. The long stretches of flat panel make warping a real problem. Stitch welding will help. By welding small spot welds, every few inches, the heat is spread out, allowing the panel to cool faster, reducing warpage. This picture shows the second round of spot welds.

22. Eventually, you end up with this, a fully welded panel with minimal warping. This also decreases burn-through. Welding the entire panel this way should take you 2-3 hours, letting the panel cool.

23. Once the welding was completed, we moved on to the filler work. The welds were ground flush with a grinder, and the paint was sanded away. You want to remove the paint from the affected area. 6 inches is nice, but you don’t always have that much room in certain cases. The warpage was contained to the new panel and did not extend to the rocker.

24. First, the welded areas were treated to a wiping of Duraglass. This fiberglass-reinforced body filler is not hydrophilic (water absorbing) like regular filler is. This makes it perfect for sealing any pinholes in the welds, protecting them from moisture.

25. We used a DA sander and some 50-grit paper to knock down the glass, feathering it in to the existing metal. You are not looking to level it out, just basic fill.

26. The next step is regular body filler. This is the hard part. You want to spread the filler thick enough to cover the warped areas, but not so thick that it will take forever to sand down. You can always add more.

27. Once it cures, the sanding blocks come out. This part can take an hour to a day or more, depending on your experience level. Here is quick tip- When blocking, you want to run the block in a diagonal motion, across the panel, then in the opposite direction, like an X pattern. This reduces the waves you will get if you just sand in one direction.