Install Floor Pan Reinforcements

Classic Tube introduces’65-’69 Mustang rear seat dual exhaust insert plates

Classic Mustangs have been getting dual exhaust conversions as long as there have been Mustangs. Exhaust shops have carelessly drilled holes and attached hangers using anemic sheetmetal screws. With road shock and vibration, screws pull out, pipes and mufflers drop, and it gets quite embarrassing. When dual exhaust systems were factory installed, Ford used stamped steel reinforcement inserts and brackets that provided excellent support. The vintage Mustang reproduction market is never short on ideas for making classic Mustangs a better driving experience. The latest are the rear seat area’s Mustang floor pan reinforcement plates that fit right into any ’65-’69 Mustang floor pan. Available from Classic Tube, the reinforcement plates not only provide the obvious, they also locate dual exhaust hanger bolt holes where they belong for easy installation. Although we weld them here, you can also install them using a strong industrial adhesive, which offers a solid bond over a broader surface area if you don’t have access to a welder.

1 Classic Mustang rear floor pans look like this with plenty of sealer and sound deadening to remove. These pans lack the reinforcement you need to support Mustang dual exhaust mufflers and tailpipes.

2 All body sealer and sound deadening must be removed regardless of whether you intend to weld or use adhesive.

3 All contact surfaces must be hospital clean for good bonding. Once you have a clean surface, use brake cleaner to dissolve any residue.

4 Where the truck pan meets the central floor pan, curl the lip up as shown with pliers or vice-grips. At the factory, reinforcement pans were spot welded to the trunk pan assembly before the three main subassemblies were joined and bucked.

5 As with any sheet metal stamping, some trimming may be required. Holes are punched for rosette (Belly button) welding. If you are going to use an adhesive, you will want to secure this panel with screws until the adhesive sets up. Generally four or five screws across the middle gets the job done.

6 Welding surfaces must be bare steel, which is easily accomplished with a wire wheel or an orbital sander. You want pure steel contact surfaces for deep penetration welds.

7 Next, the reinforcement pans are secured and the edges are dollied flat. You want all panel edges flush before welding.

8 The reinforcement pans are rosette welded with a wire-feed MIG welder in several locations for a solid bond. Again, you may use an industrial adhesive between these panels and get a strong bond. A glued joint, which is very common in aviation, is the strongest available.

9 Rosette welds are ground smooth and blended for good aesthetics – not that anyone is going to see it once the rear seat is installed.

10 Exhust hangers, sold separately, look like this. A twin stud bracket, secured with a s sheet metal screw, penetrates the floor pan. Then hanger is installed underneath. For ’65-’66, hanger studs are 12 and 6 o’clock. For ’67-’69, they’re at an angle.

11 Exhaust hanger stud 1/4-inch pilot holes are drilled dead center, then opened up to 7/16-inch holes, which gives you some wiggle room. Seal the holes with a self-etching primer before installation.

12 The studded exhaust bracket is installed using a single sheet metal screw for security.

13 Body sealer or sound deadening is sprayed along seams to keep moisture and road dust out. You want something dry to the touch when it cures.

14 Underneath, reinforcements are not visible and the installation looks factory original.

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