DIY 66-77 Early Ford Bronco Front Floor Pan Replacement

[broncosbybart]

Well, I started taking some pictures tonight. I don't have pics of the removal, but can talk through it. The reason for starting this thread is that the first set of floor pans that I ever did took forever and could have been done much easier and better than the final result.

All early Broncos have the same front floor shape. The floor pans used here are the original ‘stamped’ style that Jeff’s Bronco Graveyard sells. They aren’t an exact copy of the original floors but look very close. The original floors attach somewhat differently than the aftermarket ones used here.

To start out, several tools will be needed. At a minimum, you’ll need all the tools to remove the interior of the truck, a few 4-1/2” angle grinders, a compressor, an air chisel and bits, drills and self drilling screws, a 3” whiz wheel (pneumatic cutoff tool), and a welder (I prefer MIG). If you don’t have these tools, you will most definitely need them, along with proper safety and respiratory equipment.

The first thing you need to do is to remove the entire front have of the interior. This includes the dash, pedals, steering column, heater box, front seats, and doors (for ease of work). Once that is done, you are ready to begin!!

Both floor boards are installed from the factory using spot welds. These welds average approx. 3/8” in diameter and are a few inches apart. With the age of these trucks, it is always possible to run into a hackjob of a floor pan install by someone else. That is how this truck was. The driver’s side was original but had a patch panel welded over the front portion of it. The passenger side was completely replaced using flat steel and plate over top of half of the original floor.

To do it right, I recommend removing the original floors, rather than simply throwing on another layer. The removal of the originals is the hardest part. The driver’s side is smaller, so let’s begin there. A 4-1/2” grinder will be needed for this along with some ¼” thick grinding discs and some thin .040” or similar cutting wheels. I have found that using a spot weld cutter is a huge mistake. The reason is that you will have to spend A LOT of time drilling large holes through the existing flooring and cross members. They will end up looking like Swiss cheese by the time you are done!

So, take the grinder and a thin cutting disc and begin removing what you can. Huge word of warning- there is 1 cross member under the driver’s floor pan. DO NOT cut through it! Oh, and also- if you have an auxiliary fuel tank, you will need to remove it. I also recommend disconnecting removing the rear tank line as a precaution as well. Now, I recommend going from the underside of the vehicle and making some small cuts along each side of the cross member, just to mark where it is. You can then crawl back out and cut around the cross member from the top. From under the vehicle, everything will look like this.




You want to leave the cross member intact, along with an edge along the outside and rear to be able to weld the new floor to.


Next, cut the rear section of the floor out. Be sure to follow the ‘edge’ of the original inner rocker panel. There should be about a ½” lip that you want to follow. You don’t want to cut entirely to the edge of the floor. Do the same thing for around the rearmost portion of the floor. The section along the transmission tunnel can be cut right at the crease.

[broncosbybart]

In the above picture, the floor is obviously new. The painted sections are original. Again, you want to leave a 1/2" lip around the side and rear of the floor pan. The factory originally put the floors on the underside of these edges, but it is a lot easier to leave that alone and just put your new floor on top of those edges.
To remove the floor from the cross member, I recommend the grinder with a ¼” grinding disc. Rather than drilling a million spot welds, I grind them down and air chisel the old floor off. When beginning to grind across the surface of the floors, you can often find a little depression every few inches. These dimples are the spots of the original welds. This method usually works even on extremely rusted floors. Grind the original flooring at each spot weld. If you aren’t skilled with a grinder, go a little at a time until you get through the floor. Don’t go all the way through the cross member! If in doubt, take the air chisel and try to hammer around the spot you are trying to grind through. If it is still stuck, the layers won’t separate. If they do separate, you are done with that weld. Do this for all remaining welds on the rear side of the cross member. Since you cut the original floor along it, you can easily get the air chisel between the old floor and the cross member lip.
If you want to take a break from that, you can cut the front section fo the floor out. You can cut the floor along the front edge of the cross member. Then cut along the transmission tunnel toward the front edge of the floor. Stop when you reach where the floor begins to turn up toward the firewall. At that point, you will want to cut about 1” from the edge of the floor. Stop when you get near the firewall. Do not cut along the seam between the upper section (angled portion) of the floor and the firewall. Cut about ½” down from that seam and cut across from the tunnel to the kick panel. You can cut the floor all the way along the kick panel. When you get back down to the flat portion, leave a ½” lip like you did on the rear section. This is described as cutting counter-clockwise orientation.



In this picture you should get a good idea of what needs to happen. You will need to grind the front spot welds out of the cross member and carefully cut the top layer of floor from off of the cross member.

[broncosbybart]

More to come!

[chuzie]

Hell of a write up. Great attention to detail! Thanks for the contribution.

Sent from my Droid using Tapatalk 2

[wepuckett]

Ok I have a question on floor pan replacement and figured here would be the best place to ask it. I am using donor floor pans and was planning on just wire wheelling the edges for a clean edge to weld the replacement pans in and then having the entire body media blasted. Would I be better off having everything media blasted first or am I ok putting them in then having everything media blasted and por 15 ing the body and such? Thanks for the advice ahead of time.

William

[broncosbybart]

Personally I would have it all blasted first. BUT- blasting is probably going to run you around $1k. It really doesn't make sense to try and piece old metal back into it if you are stripping it all down. The time and effort it will take to try to reuse metal is just not worth it, except for small patches here and there. Floors are not one of those areas.

I would recommend not using POR if you blast. Use Ospho on severely rusted areas. Then use a HIGH QUALITY epoxy primer followed by your choice of top coat or bed liner, etc. I have been using epoxy from Southern Polyurethanes epoxy with great results.

[wepuckett]

Ok so cut all the bad metal out have the donor floor pans cut out, then take it all to get blasted and then begin welding. After welding use Ospho then epoxy primer and bed coat the underneath and bed inside. Please correct me if I have something wrong. The donor panels I have for the tunel and seat platform and even the bed is all in pretty decent shape and might end up changing my mind after I get them back from blasting. Thanks ahead of time for advice.

[wepuckett]

Ok let me see if I got this right, from the bottom take like a drill and pop holes next to the cross members on either side, so you know where they are. Then on the top draw lines for your 1/2 or inch edge all the way around, then with your cut off saw cut the floor pans out avoiding the crossmembers. Then use the air chisel or hammer to seperate the floor pans from the crossmembers, then carefully cut along your line to cut the final piece of the floor pans out without cutting the cross member.

Please correct me if I have something wrong with the procedure for removing the floor pans as I am trying to picture how to do this before I begin shortly.

Thanks
William

[broncosbybart]

You about have it except you will need to grind down the spot welds on the old floors before you try and separate them from the cross member. You can't just air chisel them apart without destroying the cross member. You basically have to grind through the floor pan, but not into the crossmember. Then use an air chisel as needed. Make sense?

When you've done it a few times you don't really need to locate the cross member first. Just helps sometimes. Biggest thing is to not just go crazy cutting things and cut a crossmember. I've seen it done.

[wepuckett]

Yes it does I just need to get the first round of pans out then see where the welds are better.