"Right" way to weld in floor pans?

[jdiesel33]

I am having the toe board portions on both sides of the floor pan cut out and replaced. Have talk to a few people about doing the job and have heard 2 different methods and was wondering from you guys if one is the "right" way or if one is preferred over the other. If so, why is it better? The first method is the butt weld. You cut the piece pretty much the exact size of the hole, butt it up against the existing pan then make spot welds all around about an inch or 2 apart. Then you go back and make more spot welds between the first welds and repeat that process until pretty much the whole perimeter is covered and then grind those welds down. The other method was cutting the piece a little bigger than the hole, then doing some spot welds in various places around the perimeter then using seam sealer. Hopefully I explained those accurately. I'm sure you guys will know what I am trying to talk about.Is one of these methods preferred over the other?

Thanks

[westcoastdodge]

both of those methods are the correct way,however i prefer to do the but weld and grind down to make the joint invisible

[elitecustombody]

if you want OE factory appearance ,butt weld is the way to go,lap joint is OK if you're not concerned about factory look, you can also use panel bonding adhesive and glue them in ,makes the job rust free,no grinding,welding e.t.c.   

[Troy]

I think the overlap/spot weld/seam sealer approach is a hack! I had to rip the "new" floor pans out of one car because of that. Maybe the way it was done in that case was incorrect but here's why I say that:
The new pans were set in place over jagged holes and then pounded into shape (they won't fit exactly because they are laying on top). The few spot welds were only on top between the new panel edge and original floor (not edge). This left a lump all around the patch and left a ledge under the car for water/gunk to collect and "wick" through the rest of the seam. It didn't look horrible from the top but was down right scary from the bottom. It mostly looked like someone was too lazy to trim the panel. Without a very strong weld the patch and floor twist and bend differently so any seam sealer breaks loose eventually.

A "butt" weld is easiest to blend in and hide. These cars are unibody construction so the floor is structural. Having a solid weld keeps the patch from bending and twisting separately from the floor. Depending on who is welding and what equipment they are using you'll either leave a small gap (1/16"?) or no gap at all. Typically, I think most people use a Mig and the million-little-spot-welds approach until the gap is completely filled.

However, I believe that an even stronger method is to cut the patch larger than the hole and crimp (Z bend) all the edges. This will allow a "lap" weld (or double if you weld both sides) around the entire perimeter. The bottom side can be ground flush with the floor and the top will have a ridge - but that's hidden by the carpet and padding. This requires more time and effort for fitting and may be overkill but it also cuts down the chances that you'll warp something (if you're new to welding sheet metal).

Troy

[charger2fast4u]

However, I believe that an even stronger method is to cut the patch larger than the hole and crimp (Z bend) all the edges. This will allow a "lap" weld (or double if you weld both sides) around the entire perimeter. The bottom side can be ground flush with the floor and the top will have a ridge - but that's hidden by the carpet and padding. This requires more time and effort for fitting and may be overkill but it also cuts down the chances that you'll warp something (if you're new to welding sheet metal).

Troy

hey Troy im alittle lost about how to do your last method. do you have any pictures you could post of the process? the way i do my patch panels is i cut the bad part out of the floor and leave the new piece to be installed about haf an inch bigger then the hole so it overlaps then i lay down some tack welds and finally once they are about an inch apart from each other i then lay a weld to connect the 2 spot welds together and change sides and repeat this way it keeps the heat from warping things. depending on what the project is i then either go to the bottom side and either weld the overlap from the bottom to or put seam sealer in the lap and pinch the panel tight so the sealer squeezes out and gets a better seal. is there anything wrong with this method? other then it not looking stock.

[moparguy01]

I believe what Troy is saying is you cut the patch slightly bigger than the hole, and use a flangingtool to drop the edge of the remaining floor around the hole so you can set the new price onto the lip you just made. And weld accordingly.

[Troy]

However, I believe that an even stronger method is to cut the patch larger than the hole and crimp (Z bend) all the edges. This will allow a "lap" weld (or double if you weld both sides) around the entire perimeter. The bottom side can be ground flush with the floor and the top will have a ridge - but that's hidden by the carpet and padding. This requires more time and effort for fitting and may be overkill but it also cuts down the chances that you'll warp something (if you're new to welding sheet metal).

Troy

hey Troy im alittle lost about how to do your last method. do you have any pictures you could post of the process? the way i do my patch panels is i cut the bad part out of the floor and leave the new piece to be installed about haf an inch bigger then the hole so it overlaps then i lay down some tack welds and finally once they are about an inch apart from each other i then lay a weld to connect the 2 spot welds together and change sides and repeat this way it keeps the heat from warping things. depending on what the project is i then either go to the bottom side and either weld the overlap from the bottom to or put seam sealer in the lap and pinch the panel tight so the sealer squeezes out and gets a better seal. is there anything wrong with this method? other then it not looking stock.

I believe what Troy is saying is you cut the patch slightly bigger than the hole, and use a flangingtool to drop the edge of the remaining floor around the hole so you can set the new price onto the lip you just made. And weld accordingly.

Yep, I've been sick for a week and couldn't remember the name of the tool. It basically creates a 1/4" "lip" along the edge of the metal. I thought I had a picture of some test pieces online but I can't find it. If the metal you are trying to patch has a lot of bends and curves (like some sections of the floor) it will be difficult and you'll only be able to flange the flat parts.

I still prefer the look of butt welds. I think any sort of overlap joint is ugly - and rust prone unless sealed tight. I'm sure there are good body men/welders out there that can create a strong, waterproof lap weld but none of them worked on my car previously.

Troy

[jdiesel33]

Thanks a lot fellas. Sound like the consensus is butt weld.

[jdiesel33]

Now if you were doing a small metal patch say 4" by 4" or if you were doing a major quarter panel patch, would you still use the butt weld method?

[elacruze]

Yep, I've been sick for a week and couldn't remember the name of the tool. It basically creates a 1/4" "lip" along the edge of the metal. I thought I had a picture of some test pieces online but I can't find it. If the metal you are trying to patch has a lot of bends and curves (like some sections of the floor) it will be difficult and you'll only be able to flange the flat parts.

I still prefer the look of butt welds. I think any sort of overlap joint is ugly - and rust prone unless sealed tight. I'm sure there are good body men/welders out there that can create a strong, waterproof lap weld but none of them worked on my car previously.

Troy

http://www.harborfreight.com/air-punch-flange-tool-1110.html


I bought one of these to do the floors in my pickup. Money well spent. Lip one piece up and the other down, and you can lap weld the top and bottom both. But it does not stand up to scrutiny in a very nice job like you'll want in the Charger. Your best friend for fitting butt weld pieces is patience and a very sharp set of shears.