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Restoration Tech- Replacing Floor Pans in a Pontiac Trans Am

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Besides fender well lips and quarter panels, floor pans are notorious for developing body cancer. Leaking windows and T-tops let moisture soak into the carpet, and that moisture eventually turns to rust. When buying a car, looking at the front floor pans is usually part of the routine, pulling the back seats is usually not, which can lead to an unhappy surprise when you get it home.

All is not lost, however, as most popular cars have aftermarket floor pans available, if not complete, at least in patch panel form. The actual process of installing floor pans is really not that tough, especially considering the fact that nobody is ever going to see them, which makes them a perfect candidate to learn from for the novice builder. That is not to say that it should not be right the first time.

The tools needed to perform this task are pretty common and most any enthusiast builder should have them in his shop. A quality wire-feed welder is the biggest necessity, either gas-shielded or flux-core will work, though flux-core welders cause more splatter that will need to be cleaned up. Other than that, an air compressor, die-grinder and cut-off wheel are about all you need to get it done.

One thing that most builders leave out is weld-through primer. This high-zinc content primer is formulated to withstand the high heat generated by welding and is a must for any body panel replacement work. Available at any body supply or parts store, weld-through primer will keep the rust from attacking the fresh welds and sheetmetal from rust, particularly in those hard-to-reach places like overlapped and boxed joints. Once welded, the seams should be coated with seam sealer to finish off the job, ensuring long lasting protection from rust.

To get the lowdown on how to do it right, we took our ’78 Trans AM SE to Ramsey and Son Automotive in Stillwater, OK. We watched and photographed the process and brought it to you here. By following these steps, you should be able to replace the floor pans in your ride with ease, just take your time and do it right, the first time.

1. The original floor pan in our 78 TA has seen better days, the body cancer has turned this into a regular Flintstone-mobile. Floor pans are a great place to test your welding skills. We let Toby Ramsey, of Ramsey Auto Body, show us the right way to do it.

1. The original floor pan in our 78 TA has seen better days, the body cancer has turned this into a regular Flintstone-mobile. Floor pans are a great place to test your welding skills. We let Toby Ramsey, of Ramsey Auto Body, show us the right way to do it.

2. The new replacement floor pans came in a larger section than what we needed, so we will have to trim them down.

2. The new replacement floor pans came in a larger section than what we needed, so we will have to trim them down.

3. Toby cut out the offending section, being careful not to cut the floor bracing. A cut-off wheel is the best plan of attack here.

3. Toby cut out the offending section, being careful not to cut the floor bracing. A cut-off wheel is the best plan of attack here.

4. Using the old section as a guide, Toby marked the new panel slightly larger and trimmed the panel with a cut-off wheel.

4. Using the old section as a guide, Toby marked the new panel slightly larger and trimmed the panel with a cut-off wheel.

5. The 2 sections together show that the new section is slightly larger, about 1\4 inch on each side. This makes for a nice overlap joint. A butt-joint places the 2 pieces flush, end to end, which is a more difficult joint to create and not necessary for a floor pan.

5. The 2 sections together show that the new section is slightly larger, about 1\4 inch on each side. This makes for a nice overlap joint. A butt-joint places the 2 pieces flush, end to end, which is a more difficult joint to create and not necessary for a floor pan.

6. The remaining floor pan was cleaned up with a die-grinder and a 36-grit sanding disc. The removes any remaining surface rust and provides a solid area to weld to.

6. The remaining floor pan was cleaned up with a die-grinder and a 36-grit sanding disc. The removes any remaining surface rust and provides a solid area to weld to.

7. The panel was sprayed with Rubber-Seal weld-through primer on the outer edges.

7. The panel was sprayed with Rubber-Seal weld-through primer on the outer edges.

8. The interior section of the floor pan was sprayed as well.

8. The interior section of the floor pan was sprayed as well.

9. The patch panel was tack welded in place about every 2 inches. Once it was tacked in, Toby stitch welded, which is done by placing tack welds every 2 inches until the entire panel in welded. This ensures a warp-free repair. The pie-cuts at the corners were stitch welded as well.

9. The patch panel was tack welded in place about every 2 inches. Once it was tacked in, Toby stitch welded, which is done by placing tack welds every 2 inches until the entire panel in welded. This ensures a warp-free repair. The pie-cuts at the corners were stitch welded as well.

10. Once the panel was fully welded in place, Toby applied seam sealer and sprayed the entire floor with undercoating, resulting in a nice, clean repair. No more Flintstone action here.

10. Once the panel was fully welded in place, Toby applied seam sealer and sprayed the entire floor with undercoating, resulting in a nice, clean repair. No more Flintstone action here.

 

Sources

Ramsey Auto Body

405-743-3107

About Jefferson Bryant (201 Articles)
A life-long gearhead, Street Tech Magazine founder and editor Jefferson Bryant spends more time in the shop than anywhere else. His career began in the car audio industry as a shop manager, eventually working his way into a position at Rockford Fosgate as a product designer. In 2003, he began writing tech articles for magazines, and has been working as an automotive journalist ever since. His work has been featured in Car Craft, Hot Rod, Rod & Custom, Truckin’, Mopar Muscle, and many more. Jefferson has also written 5 books and produced countless videos. Jefferson operates Red Dirt Rodz, his personal garage studio, where all of his magazine articles and tech videos are produced. You can follow Jefferson on Facebook (Jefferson Bryant), Twitter (71Buickfreak), and YouTube (RedDirtRodz).

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