1968 Firebird floor pans replacement


I hate giving a product a free plug, but I believe this to be essential during a complete restore. Every piece that you take apart will show some kind of rust, even if it's just surface rust. The sand blasting took care of everything exposed; now your getting into the body. EVERY piece that I have taken apart has resulted in cleaning the piece and then treating it with POR15.

BEFORE cutting or removing your floor pans, I would strongly advise you to get some measurements. The main point is the sub frame bolt hole that comes up under the seat frame support. Get at least two points that are factory specific and measure to the center of that hole. Write this down and save it for later. MAKE SURE you inspect underneath the pan BEFORE you start cutting. You will find the firewall support under the toe, and at the rear seat, be careful of the front spring support of the rear leaf.

Also, once you get the seat frame support, and the seat brace (that holds the sub frame nut) removed, lay your new (toe to rear seat) pan in and use a soap stone or other marker to outline the new pan. Make sure it lays in as flat as possible on top of the old pan.

This is how "I" did it and maybe the "pros" have a better way. I measured 2 inches below the outline and drew a parallel line all the way around. This is the line that I cut. Before I did, I made markings above the outline and took measurements so when the new pan went in, I could make sure it went in with the proper height by measuring from those markings. Plus, if you don't have to cut the seat belt anchor out, leave it and just measure for your new pan to leave it exposed.

After cutting the old pan out, here is the new pan laid into place.


I measured the sub frame bolt hole, measured from the markings above to ensure its proper height, and then I just tacked it into place.

ALL after market items are very CLOSE to the original. Some better than others. The main point here is that you mock in the seat brace and check your measurements, and then lay in your seat frame support and measure it as well. Once you get it all set in place, and you feel very confident that it is correct, take the seat frame support and seat brace out and do it again. Then, if it all goes back in the way it should, remove them and complete the welding of the floor pan. My method of welding it in was this; I seamed welded for one inch every 6 inches around the pan. I then used my 3/8 inch plug weld cutter and cut a hole (in the new pan only) between the one inch seams about one inch below. If you remember, I left at least that much of the floor when I cut it out. I welded those holes (plug weld) all the way around. I am very confident that the strength is included with this method, and I don't have very much warpage as well. Be sure to do this under the toe where the firewall frame comes down underneath the floor pan. I also laid a one inch bead all along the rocker every four inches. When I'm done with everything topside, I will lift the car and go underneath to finish up welding on the bottom side.

Time to lay in the seat brace. Don't be afraid to use a hammer to get it to lay in the way it should. Just make sure the sub frame nut is where it is supposed to be. Measure it!

Once laid into place, I just tacked it in, and then laid the seat frame support over the top to ensure its fit. I also used a bullet level to make sure the seat frame support was level. You don't want to go down the road leaning to one side. Front to rear has a natural slope to it, but not side to side. All looked good, so I removed the seat frame support and seam welded and plug welded the seat brace in.

Next came the seat frame support. I laid it in and took the measurements. It laid in pretty good, but the rear of it did not fully rest on the floor pan. Again, after market parts are very CLOSE to the original. I got the seat support frame laying pretty good, then I tacked it into place. I took a floor jack with a piece of wood and carefully put pressure up under the floor pan and that brought the two together nicely. It was only about a 1/4 inch, but I wanted them to match flat with each other for a proper fit and weld. Once again I used the bullet level and all looked good. I finished it off with seam and plug welding. I have my own theory about welding in floor pans. If interested, click here.

Here's the final product.


Off to the other side. Hope your project is coming along great!

O.K. here we go! The right side went pretty smooth with the exception of the seat frame support. It fought me every which way it could. This supports the above statement that after market parts are CLOSE, some closer than others. I have bought everything through the same company and all has been really good, but this one item gave me heck! You will inevitably come across one. You just work with it. Make it do what its supposed to. Remember, you are in control.


I will now order the lower patch panels for the front fenders, and start on smoothing out the right half of the firewall since I will be installing an after market a/c system. I'm looking at Vintage Air and Classic Air. Don't know which one yet.



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