Taking apart the floor/firewall seam

Whats the best way to get the firewall/floor seam apart for the purpose of replacing the front floor seam.

I have not seen many details on this.....

Sounds like you are replacing the floor pan? Probably doesn't matter much what car... After drilling the spot welds on the frame and getting as much of the pan out as possible, I cut the pan next to the seam, being very carfeul not to cut lines, T-bar, frame etc that are under it. Cutoff wheel, sawzall, whatever you can get it with. Then you can get to the flange and grind the spot welds off.

demondreamer said:

Whats the best way to get the firewall/floor seam apart for the purpose of replacing the front floor seam.

I have not seen many details on this.....

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Ok so that seam is just spot welded and seam-filled?
It's nothing more than 2 90 degree bends spot welded together?
I thought it might me some kind of channel hem like on hvac duct. There is a lot of seam fill in mine almost a quarter inch bead

Yup, pretty much the whole car is spot welded. And yes they were generous with the seam goop...

Mine already had the filler removed, but the firewall fold has a 90* lip that the floor pan fold sits on. Mine was just spot welded. Drill them out in the engine bay and wheel well. My dart had 5 or6 on wheel well side one the same on the engine bay.

zkx14 said:

Yup, pretty much the whole car is spot welded. And yes they were generous with the seam goop...

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And this generosity is what caused my quarter panel/trunk extension to rust. There was a big blob of the crap between the two of of them. Any moisture that got down in there just hung around.

Don't know how much you have pulled apart.... I'd only drill them if you are going to be able to weld them there. I did drill some from fender side, a few of them were gone -had a section of rusted firewall that I had to replace. I didn't have engine out at the time so I don't think I was able to get on them all. I just welded some of the seam from inside

Bunker45 said:

Mine already had the filler removed, but the firewall fold has a 90* lip that the floor pan fold sits on. Mine was just spot welded. Drill them out in the engine bay and wheel well. My dart had 5 or6 on wheel well side one the same on the engine bay.

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Thanks for the input, the motor, trans and dash assembly are out of the car as well as the entire interior

I don't have it at my house due to just having moved in and lot's of our stuff is in the garages in boxes still. The car is at a local self storage place, and management is very cool about allowing work on the car. They even hooked us up with a strong 20 amp outlet. We can run a grinder and the Harbor Freight fluxcore welder with no issues.

Right now due to other family obligations we only work on the car Wednesday nights.

It was after dark when we wrapped up this week and I didn't get a good look at the seam. I got the passenger front area all cut out with a 4" thin cutoff wheel in a grinder and chiseled the spot welds apart. No damage to fuel lines, emergency brake cable or anything else.

I'm planning to start fitting the new pan from the corner where the firewall meets the inner fender and fitting the firewall seam and along the door jamb first. I was going to cut the new pan 1" over where it will meet the tunnel and vertical rise that begins just under the front edge of the seat. I then was going to tack the pan in and re-cut through the pan and the existing tunnel/floor structure to create a butt seam. Then tack and stitch weld it in.

Do I spot weld it to the frame members before or after the perimeter?

Am I aimed in the right direction?

There's something to be said for giving yourself enough room to move. I cut back far enough from the rocker and cowl seams to allow my drill and spot weld cutter... Then centerpunch and drill th floor layer, grind, hit with weld-through primer, and fit the pan/patch. Sometimes trying to keep the patch small and tidy creates a lot of drama and I'd rather replace more and have less evidence of it showing.

I did frame first. Be real careful how much you trim. I thought I was leaving at least an inch till I pushed it tight to the frame and it nearly slipped below the tunnel at the back corner. Once I had it close I vice gripped the front flange together and set a cinder block on it and crawled underneath. make sure you have contact everywhere needed - then drew the frame and all the edges on with a sharpie so I knew exactly what I had. Then I picked the high spots on the frame and drilled them next to my lines for my fill welds. A little more trimming and tack it in. Recheck and weld it.