How to weld a car floor panel??

[Sammy]

I am currently in the middle of cutting out rust from a car floor pan, and will need to know soon whether i can do spot welds or do i have to run a bead?

Right now i am thinking that i will first of all:
1.Cut the sheet metal to size.
2.Shape it to the original floor pan.
3.Drill holes through the new floor pan every 1" around the perimeter.
4.Set it in place with a 1/4" overlap.
5.Fill the holes with a burst of MIG.
6.Then seal the seam with sealer.

Does this sound good? I am thinking of using 20guage or 22guage sheet metal.

Any advice or tips/help would be greatly appeciated.

Thanks in advance!!!

[BC Iron works]

mig weld do 4" at a time and move around

[wrenchnride247]

You can weld in panels by over lapping and plug welding them, but this method is prone to trapping moisture between the panels. The best way to do the over lap style repair though is make shure you have good metal to weld to on the original panel. Then, strip to bare metal on both panels anywhere they contact each other. Next, make your holes in the replacement panel about one inch apart around the perimeter. To help protect against rust coming back between the panels use a "weld thru" primer (3M or SEM brand are great) on the areas where the two panels will overlap. Using a few sheet metal screws to the hold the panel in position while you weld it up is handy. The wire size for MIG welding this should be .023 ga. and LOW heat (its best to practice on scrap of the same gauge to get heat and wire speed right) do two or three plug welds then move to other side of panel and do some more then back to other side while welding to keep heat down. Finally, clean any weld thru primer off that you can see (most of them don't work with anything over top of them) before adding seam sealer (on both sides of panel) and paint.

[Sammy]

Thanks alot for the advice! Is it best to complete a full seam in total around the new piece if i decide to do it that way? Anymore pictures would be a great help since i can see a whole lot more that way.

Thanks

[Sammy]

I have another question. What guage sheet metal should i use? Is there any where that sells ribbed steel like an original floor pan?? I am on a tight budget right now so i don't want to be ordering $100 REPLACEMENT pans which i will have to cut anyway. Sorry i keep asking questions and no showing of the actual work. My camera is getting fixed righ now but when its back i will show pics.

Thanks in advance for any input.
Pictures are great as well.

[davinci2010]

If you don't buy a replacement floor pan, you will not find the metal ribbed to match the factory piece. People making the patches from raw metal stock work the metal to match the factory profile themselves. When you weld, stitch weld the replacement a few inches at a time and alternate sides after each stitch is finished to keep the heat from warping the metal. Try to match the thickness to the surrounding sheet metal. Some people "hammer weld" patches in. After welding a stitch, back the weld up with a dolly on the back and hammer the weld seam flat. I've never found this to be required, but I know some people that restore cars for a living and swear by it.

[nocheepgas]

What kind of car are you working on? You might get a replacement panel from a wrecking yard. Plenty of rust free ones here in Arizona.

[Sammy]

Its a Volvo P1800. Not too many up my way. I have wondered about it though.

[nocheepgas]

You may want to do a search on the ner and see if you can find one at a wrecking yard.

[Coburn_Performance]

Its a Volvo P1800. Not too many up my way. I have wondered about it though.

Hi Sammy,

I'm sure I can answer a bunch of your questions...mostly because I've built a few Volvo 122's - by the way, join the rest of us at the Calgary Volvo club http://www.calgaryvolvoclub.com/. Olof from Vintage Import Parts http://www.vintageimportparts.com/can get you factory replacement panels for your 1800 that are the correct gauge and fit great. I've had very good luck with Volvo replacement panels as they are made to the factory specs rather than just holders for Bondo.

I butt weld just about all panels on body work as that gives the best long term results, and I have done it with 0.035" wire by linking tacks - initial tacks set around 1" apart first. More tacks = better. If you want to run stringers you can step down the wire size. Like this:


When the replacement panels have a spot weld flange, I punch 1/4" holes in the panel and plug weld the panels - if I've got more flange, I'll use 3/8" holes. Then use urethane seam sealer to seam up the weld area front and back after it has been epoxy primed.

Here are a few of the Volvo's I've done.

Fabrication of a friends car in Calgary.