Floor Pan Repair

jelco

jelco

Promoted Users
I need to replace the floor pan of my 64 El Camino. Seems like a daunting task but I’m going to give it a try. I bought a Blair spot weld cutter and buying full left and right halves of the floor pan. It also looks like the rear vertical panel may need to be replaced, or patch it.
I was reading this other post about seam sealer but confused about a few things.

which seam sealer??? HELP

I have a 67 Chevelle I am working on. Lots of new metal. Currently I am about ready to epoxy the underside of the floor and trunk pan as well as the wheel tubs. I plan to shoot SPI epoxy, seam seal, then shoot Upol Raptor Liner over it all. My question is which seam sealer should I use? 1K...
www.spiuserforum.com
Is 2k seam sealer worth the investment?
Don’t you want to seal from above and below?

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But the bottom is typically sealed with truck bed liner or something similar, so the top and bottom would be sealed.
 
Epoxy typically gets into crevices that seam sealer doesn't (as well). So for any pinch weld seams or lapped factory seams like you'd see in a floor pan seam, I'll mix up some epoxy and just hand brush the areas until the flow checker drips on the bottom side indicate coverage. Then clean off the drips once the epoxy has set a bit, and go back with your seam sealer after epoxy has set up sufficiently. I've also been told I'm anal retentive, so take that into consideration … ;)
 
jelco said:
But the bottom is typically sealed with truck bed liner or something similar, so the top and bottom would be sealed.
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Good point. I think there may be a little overthinking going on here. Typically cars built to this level rarely see rain, let alone salt. What sort of timeframe are you expecting the build to last? Are you building a driver or a Smithsonian museum piece? Do you want the car to outlive you and you children? The engineer in me makes me a firm believer in the law of diminishing returns. More and more effort, time and money yielding smaller and smaller returns...

I’ve seen guys try to seam seal the bottom edge of a vertical floor to rocker pinch weld. This makes little sense to me.

That being said I think I’ll use Robert’s technique on my next floor installation.

Don
 
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what’s a flow checker? So you’d weld, epoxy, seam seal then epoxy again?

I’m just trying to learn the right way to do it. Some 50 year old cars don’t have as much rust as mine. The rear window is a problem area so I need to fix that too. Done right I think it could last many years without holes in the floor pan even more if it’s garaged and taken care of.
 
I think his flow checker is when it starts dripping.... Similarly I call runs viscosity test strips....

Pretty sure he is brushing the epoxy into the pinch welds etc before seam sealing.

Don
 
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jelco said:
what’s a flow checker? So you’d weld, epoxy, seam seal then epoxy again?

I’m just trying to learn the right way to do it. Some 50 year old cars don’t have as much rust as mine. The rear window is a problem area so I need to fix that too. Done right I think it could last many years without holes in the floor pan even more if it’s garaged and taken care of.
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The flow checker, as Don stated, is basically seeing paint come through the opposite side. Similar to what we did here on the Biederman fenders... Two pieces came together in a highly susceptible water prone area, so we used SPI epoxy and a brush, and when you brush against the flange it will tend to wick the paint into the gap between. We continued that process until the epoxy came through the other side.

After grinding the welds, John brushed some SPI epoxy in the lapped panels to seal them up..


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It's hard to tell if you have good coverage when you can't see between the overlapped panels, but if you have paint running through, it's about as good as we can get.
 
After waiting nearly a month for shipping I got one half floor pan from Meyer distribution, still waiting for the other half because of their error. My rusted out areas are above and below the cross braces.
Whats the advantage of replacing the full half floor pan compared to cutting square holes on each side of the cross braces and butt welding?
I haven’t quite figured out how the original floor pan was connected to the body. I know it’s spot welded to the rocker panel but it looks like it raps around, outside of the frame and is connected to the rocker panel.
See photo. From the ground looking up, left side is rocker panel, middle is floor pan, right side is frame
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How much 2k seam sealer would be needed for a floor pan? A total of 14oz or 400mL, maybe 600mL?
 
I use a lot of the 8411. I like it better than any of the 3M sealers i've used. I really believe 1 would do a floor pan, but you could get 2 to be safe.
 
Ok thanks. I also ordered SEM 40377. How does it compare to IES 8411?

I started putting the floor in. Is there a better way to prep it for butt welding to the middle section other than taking it in/out a hundred times?
 

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I finally got the floor pans welded in. I’m planning on brushing on epoxy primer on the welds and rocker panel seam then putting 2k seam sealer on all my welds (inside and underside) then spraying with epoxy primer.

Whats a decent diy truck bed liner option for the underside of the floor pan? Gravel guard, herculiner, monstaliner?
I also need to sound deaden the inner wheel wells with something.

I’ve heard of coating the inside of the floor pan with truck bed liner then applying Dynamat but that’s seems pointless to me.
 
jelco said:
I finally got the floor pans welded in. I’m planning on brushing on epoxy primer on the welds and rocker panel seam then putting 2k seam sealer on all my welds (inside and underside) then spraying with epoxy primer.

Whats a decent diy truck bed liner option for the underside of the floor pan? Gravel guard, herculiner, monstaliner?
I also need to sound deaden the inner wheel wells with something.

I’ve heard of coating the inside of the floor pan with truck bed liner then applying Dynamat but that’s seems pointless to me.
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I like SEM urethane bedliner. It has a shiny finish and doesn’t hold dirt.

Best way to deaden wheel well noise is Dynamat on the inside followed by a layer of jute. Works great.

Don
 
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