The floor in the ’73 Duster we used for this story was marginal. And install it with a lap weld. Mustang 360; Super Street.
1965 Mustang Restoration
Floor pan replacement for this 1965 Mustang restoration, is one of the most common tasks faced by Classic Mustang owners and restorers. Like most classic cars, the Ford Mustang had great sheet metal and lousy rust proofing. Ford seemed more intent on sealing spot weld seams for immediate water proofing of the interior than on preventing long term rust damage.
Classic Car Rust
If you own any other classic muscle cars, you'll also know the drill.
The Camaro, 55 Chevy, Chevelle, Charger and others all share the same fate at some time or other, a need for floor pan replacement. (And you thought the dealer installed undercoating was just an unnecessary profit taker)!
My 1965 Mustang has fared better than many pony cars, but there's still floor pan replacement in it's immediate future.
While replacing the floor pans is time consuming and isn't particularly fun, it's not all that difficult to do.
If you can't do your own welding, or can't find a friend to attach the pieces, you can at least do the prep work and save some cash.
Step 1. Assess the rust damage
The rust in my floors, showed up in two ways. The easy part, were a few obvious rust outs. The second ones showed up when I sand blasted parts of the toe panels from the wheel well area.
This showed up many small pin holes on the driver's side panel and a few small ones on the front passenger side that I'd originally thought were rust free. (Oh well....)
Step 2. Remove the rusted floor pans
Whether you use a cut-off wheel, a saws-all or other tool to remove the old floor sheetmetal, it's important to first decide what gets removed and what stays.
Just because you buy the sheetmetal floors as a unit, doesn't mean that you need to use all of them. For one thing, the replacement floors don't always fit like an OEM piece and you can still make a good looking floor pan replacement with a partial piece if you're careful.
To complicate things, my 65 Mustang, had an ugly heavy gauge steel patch panel welded onto the driver's front floor area. underneath, was a chewed up, sharp edged mess, where the old metal had been removed.
This resulted in some struggling to remove metal at the welds along the insides of the rockers. First came removing the patch panel and welds. Then came removing the jagged metal from the original floors and the lips still spot welded to the rockers. I thought I was done, but a little more digging and poking with a screwdriver revealed that there was more rustouts higher up, so off came even more of the original toe board... The toe kick area wasn't fun, because of the combination of original toe kick metal, a strip of original floor pan, the hard metal weld and the welded on piece of patch panel. (Whew!)
Warning: The driver's side toe panel near the gas pedal has the brake lines attached flush to it. So don't cut through without looking or you'll have a few more parts to be replaced!
I decided to keep the good sheet metal between the transmission hump and the front crossmember for two reasons. The first, was because it kept the frame stiff with the old floors cut out. And secondly, because the original metal was in good shape and a heavier gauge than the panel replacing it.
My seam will be directly on the frame rail flange, for an invisible fit and a very solid seam. Then, for a better fit and to make the seam below the seat platform fit tightly, I notched the rear side of the panel to allow it to slide below the platform and stay in place while I fitted the front edges of the replacement panel.
Seat Platforms
The Seat platforms were in reasonably good shape, needing only a small patch on the forward edge. And floor pan replacement for the rear portion was a much simpler job.
Rear floor pan removal
Again, it's a good idea to think about what goes and what stays. For a better appearance below the car, I chose to make the seams as high up the bend in the rear of the floor pan as possible. It's also the strongest part of that floor, with it's compound curve.
And I did the opposite where the floor meets the transmission tunnel. In this area, I cut out the old floor below the machined bulge, where the seat belt backing plate is attached. This saves me having to get under the car, figure out where the old hole should have been and attach the backing plate to the new floor panel.
It also allows me to have a very solid welded area around the backing plate.
Now it's time to test fit the floor pans. The old adage 'measure twice, cut once' is sound advice. Once all the pieces have been test fitted it's time to clean dress the areas with a wire wheel and grinder to remove old paint, rust and dirt and coat the areas with a cold galvanizing weld through primer.
Note: DO NOT use panel bonding adhesives. While it's fast, these floors are structural and panel bonding materials are for non structural pieces.
When that's done, it's time to weld them in place and then apply a sealer to the floor pan replacement joints to keep moisture out and at the same time, blend the repaired area with the original floors.
Next ... Part 7 Floor Pan Replacement Part 2
The floor pan removal and replacement continues in Part 7
Restoration Sections
Part 1 - Mustang Restoration Index Part 2 -Resurfacing Minor Irregularities Part 3 - Rear quarter panel repairs Part 4 - Inner Fender Refinishing and Repair Part 5 - 1965 Mustang Restoration Part 6 - Floor Pan Replacement Continued Part 7 - Headliner Replacement Part 8 - Mustang Dash Restoration Part 10 - Priming and Painting your Mustang Part-1 Or find what you're looking for fast with the search box below. Return from floor pan replacement to Ford Mustang home
Floor Pan Replacement continues. Trimming the new floor pans is time worth taking to get a good professional and tight fit. The rust has been removed and it's time to trim the floor pan pieces to what you need. So how do we know where to trim? By making a template.
Since trimming metal pieces is harder to do than cardboard, I use pieces of scrap cardboard, cutting and taping them together to get the fit I want.
Once I'm satisfied with the fit, I transfer the shape onto my new floor pan replacement piece and remove the excess sheet metal.
Using clamps, wood and a small bottle jack, I'm able to position the pieces into place for tack welding. You'll notice the small welds in the middle of the toe board panel. These are the 'spot welds' to the sub frame below.
Since I'm using a mig welder, I've drilled small holes through the toe kick panel and welded through the steel to join the pieces in the OEM factory style.
What I'm not doing, however is attaching the floor pans this way. The seams will be fully welded and then sealed with seam sealer for a 100% joint.
The toe board or toe kick is first rough cut, then trimmed to best fit the floor pan replacement sheet metal.
If you are working on a 1965 Mustang convertible, or newer classic Mustang, you may be wondering why I haven't mentioned torque box replacement.
That's because the early Mustangs only featured the structural reinforcement known as a torque box on the convertible.
Later cars all have them and you can count on torque box replacement if you have rusty floors to repair.
Sealing Mustang Floor Panel Seams
When the pieces fit to my satisfaction, I continue welding them to the exposed floor, making sure that I've sprayed a cold galvanizing, weld through primer to help prevent future rust from destroying my floor pan replacement efforts.
On the exterior (wheel well area) The welded seam has been placed to make for an easy to finish and hard to spot repair.
And yes, the panels have been welded below and seam sealed for a clean and rust proof floor pan repair.
The previous owner, wasn't so kind, leaving me with jagged ugly metal to remove. It looked like a really big dog with very strong teeth ripped the old panel out with his teeth!
Rear Pan Before
Test Fitting The Replacement
Sealed Floor Section
OEM Floor Pan Look or Good Replacement
Here's a way to make your seams disappear for that smooth OEM floor pan look. It's also waterproof.
I use a short strand fiberglass filler after the floor pan replacement panels have been welded, when I want to blend the repaired floor area into the existing sheet metal.
If you try to do this with ordinary body filler, you'll end up with a big ugly cracked and rusted mess in the not too near future.
So bite the bullet and invest in a good fiberglass filler like duraglass or other filler.
It's hard on sanding discs, but it's rock hard and tough.
Patcing Floors
Sometimes a full panel is overkill.
The front passenger floor in my 65 Mustang coupe was really good, as was the rear floor area, except for a couple of small pin holes.
Now, I could have just filled over these holes, but we both know what's going to happen don't we?
That's right, not long from now, when we'd be expecting to be driving the newly restored little gem, we'd be getting that brand new carpet wet.
Yup. Little pin holes mean thin metal and another piece of floor to replace soon. So why not now, when the welder is out and the new carpet isn't yet in?
After a couple of quick cuts with a cutoff wheel, the offending rusty metal was removed and then used as a template to cut a new floor pan replacement patch piece.
A little later and wham! New solid metal. No future problems.
Final Floor Panel Replacement Finishing
Show finishing is different than a daily driver finish. I build more classic Mustang cars for driving enjoyment than car show trailer queens, and what you see in this particular 1965 Mustang restoration is, designed for long lasting street use. A show finish takes a tremendous amount of time and money and is designed to mimic exactly what you'd see if you were to have taken a classic mustang off the assembly line and examined it.
An original Mustang was not designed to last 40 odd years. Rust proofing? What's that? What you'll see is a whole lot of body color paint and the odd spray of black sealer, designed to keep out very little.
For a weekend driver or an everyday fun car, I think the way to go is to seal it tight like a drum!
You're not done yet!
It's just as important to chip off all that old dried out sealer on the good metal and re-seal it with a new coat of brushed on seam sealer. (you did that right?) When I've sealed the seams, I'm coating the entire interior floor with a heavy coat of rubberized rock guard.
It looks good (and then it's covered up) and it prevents a wet carpet from later turning into a hole in the floor ! Or if you want to do a compromise between show car and driver car, you could opt for a rust proofing sealer like was used on the inner wheel wells, before the under coating was applied.
This will give you a nice smooth finish that keeps water out and adds rust killing ingredients, while allowing you to paint the surface in the original body color. Ready to start your own floor pan replacement or restoration? Check out my all new....
Easy Floor Plan Replacement Guide
Whether you're a novice or well seasoned in other projects, my new in depth, downloadable Easy Floor Pan Replacement book clearly guides you step by step from start to finish. And it's coming early May 2012.
Subscribe to the RSS news feed (located below the listings to your left), or check back here soon, for the link to all the information you'll need to get yours.
Cheers! Bruce
Restoration Sections
Part 1 - Mustang Restoration Index Part 2 -Resurfacing Minor Irregularities Part 3 - Rear quarter panel repairs Part 4 - Inner Fender Refinishing and Repair Part 5 - Mustang floor pan replacement Part 6 - Floor Pan Replacement Continued Part 7 - Headliner Replacement Part 8 - Mustang Dash Restoration Part 9 - Trunk rust repair Part 10 - Priming and Painting your Mustang Part-1 Still looking? Use the search box to find more information. Return to Ford Mustang Home