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Butt weld or lap and spot weld new floorpans

chico68

Jr. Member
Joined
Feb 21, 2011
Messages
83
I am replacing my floor pans with some OEM style pans from wildhorses. I would like to butt weld for a clean original look. Has anyone used this method or are most people lapping it over existing sheet metal and using spot welds and seam sealer?
 

grant_71

Bronco Guru
Joined
Aug 6, 2002
Messages
1,933
Are you lapping over existing floor pan? or butt welding to existing floor pan?

The original floor pans are lapped over a flange on the rocker and then spot welded there.
 

Pipehitter

Full Member
Joined
Jan 18, 2010
Messages
152
Loc.
Clintonville WI
I plug welded all of mine in place, but I removed the complete floor pans front to back and cleaned up the support braces underneath and then plug welded the pans to the braces. The floors were set up for some overlapping when installing them, so not quite sure which areas you are referencing for butt or lap.
 
OP
OP
C

chico68

Jr. Member
Joined
Feb 21, 2011
Messages
83
I will spot/plug weld on the rocker and floor supports but am unsure whether to lap over the metal on the tunnel and where the sheet metal goes up on the seat platforms as well as toward the firewall. My rust wasn't bad so my wild horse pans go toward the firewall about 6 inches.
 

bad 68

Sr. Member
Joined
Jul 1, 2010
Messages
921
Loc.
Northest Washington
I would lap them by about 1/2 inch. Spot weld every inch then go back and continuous weld the whole pan in. just spot welds only will let moisture in under your carpet. There's no surefire way to cut out the old floor pan and the new panels to fit so close as to make a good joint for butt welding. Clean up your welds with a flapdisc and seal the lap from underneath with non hardening seam sealer.
 

crews44

Sr. Member
Joined
Sep 11, 2008
Messages
384
Loc.
Mullica Hill, NJ
IMG00009-20100815-1207.jpg

Might be hard to see but this is how I laid them out before plug welding them. I overlapped the onto the tunnel. It would be awfully time consuming and difficult to butt weld. I will be using a bunch of seam sealer......
 

iwlbcnu

Bronco Guru
Joined
Nov 1, 2001
Messages
3,341
At the tunnel, rear rise and firewall I butt welded mine to look more fiinshed and original. Think about why the truck rusted in the first place, usually where 2 seams overlapped. No matter how you prep or treat, eventually moisture will collect.
 

mavereq

Bronco Guru
Joined
Feb 19, 2009
Messages
2,092
on my next project i'm planning to use 3m panel adhesive on all the spots i overlap. the plan is to use self tapping screws to hold them in place and then spotweld the holes shut after the panel adhesive cures. the panel adhesive should help keep moisture out.
 

allenfahey

Bronco Guru
Joined
Mar 18, 2004
Messages
2,672
The correct way is to spot weld them in. Prime then use seam sealer. The seam sealer they used 40+ years ago isn't todays seam sealer. The seam sealer we use today is 100 times better. It doesn't crack and shrink like the OEM sealer.

Mavereq, you can use panel adhesive and the small self tapping screws but I wouldn't weld the holes up. If you use small screws just seam seal over them. If you weld them the adhesive will release.
 

mavereq

Bronco Guru
Joined
Feb 19, 2009
Messages
2,092
The correct way is to spot weld them in. Prime then use seam sealer. The seam sealer they used 40+ years ago isn't todays seam sealer. The seam sealer we use today is 100 times better. It doesn't crack and shrink like the OEM sealer.

Mavereq, you can use panel adhesive and the small self tapping screws but I wouldn't weld the holes up. If you use small screws just seam seal over them. If you weld them the adhesive will release.

makes sense. i wondered how the adhesive would handle heat.
 

Scoop

Contributor
Have Bronco, Will Travel
Joined
Feb 1, 2006
Messages
10,581
Loc.
Cuchara, CO
The correct way is to spot weld them in. Prime then use seam sealer. The seam sealer they used 40+ years ago isn't todays seam sealer. The seam sealer we use today is 100 times better. It doesn't crack and shrink like the OEM sealer.

Mavereq, you can use panel adhesive and the small self tapping screws but I wouldn't weld the holes up. If you use small screws just seam seal over them. If you weld them the adhesive will release.

Allen, will a bedliner like Line-X or Al's Liner adhere to the seam sealer?
 

allenfahey

Bronco Guru
Joined
Mar 18, 2004
Messages
2,672
Allen, will a bedliner like Line-X or Al's Liner adhere to the seam sealer?

It adhere's to factory seam sealers in the beds of pickups. I would of coarse wait till it fully cured and might even prime it. Sand it and spray away.
 
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