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Putting in 2 half floors


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Hey guys,

I bought 2 half floors to cut out patches for my floor but I'm thinking about putting both halves in completely. Are there any specifics I should be aware of when replacing half a floor at a time? And is it doable with the car on its wheels? The engine is also still in, should I put any form of support anywhere?

Thanks for any pointers you may have.

Vincent.

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If you’re doing one side at a time and the car is on its wheels you should be ok. I don’t think you would need any extra bracing. I changed mine 1 at a time without anything moving. Just be careful when cutting them out that you don’t cut into the floor support or torque box. Other than that it’s pretty straightforward. Lay your new pan in, trace around it and cut out old pan. Leave a nice 1” lip or so if you are doing a lap joint. If you are doing a butt weld , I would zip screw new pan in place and use a body saw and cut through both pieces for a perfect fit. I usually cut a few big hunks of the floor out first to get some of the stuff out of the way before fitting.  Pretty easy job if you take your time. 

Kevin
1971 Mach 1

408C Stroker - C4 w/3,000 stall - 8.8" Rear w/3.73's - Disc brakes all way around.

 

 

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15 minutes ago, midlife said:

Remove any glass, as it will be damaged from welding and grinding splatter.

A lot of times I cover the windows with that thick brown packing/wrapping paper.  It deflects sparks nicely. 
But yes,  you need to be careful the sparks can mess glass up pretty easily. 

Kevin
1971 Mach 1

408C Stroker - C4 w/3,000 stall - 8.8" Rear w/3.73's - Disc brakes all way around.

 

 

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The car is completely stripped, I can splatter away without worries :-)

I believe the only butt welds are against the tunnel and under the back seats. The front, outsides, seat riser and frame rails etc have spot welds?

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5 hours ago, Vinnie said:

The car is completely stripped, I can splatter away without worries :-)

I believe the only butt welds are against the tunnel and under the back seats. The front, outsides, seat riser and frame rails etc have spot welds?

Where the butt welds will be is up to you. If you're not comfortable with butt welds or if you don't mind lap joints, then technically  you could replace the floor pans with no butt welds.  Just overlap the new pan about 1" and punch holes around the perimeter and plug weld it into place, then seam seal everything.  

The spots weld you will have to drill out will be on the floor supports/frame rails. If you overlap the toe board it isn't necessary to drill out the spot welds. Same with the floor to rocker joint.   If you are reusing your seat risers then you need to drill those spot weld out carefully. If your replacing the seat risers, then cut them out and discard. 

If you don't want to drill all the spot welds out, there's an easy trick to help speed up the process. Cut the floor pan out close to frame rail, rocker, toe kick, ect.  Leave a strip of the metal with the spot welds.  Then go back with a grinder and grind the spot welds down very thin. Then go back in with an air chisel and nice sharp chisel bit and get between the rails and pop the spot welds loose.   The floor pan is much thinner than the frame and you are less likely to damage the base material with the air chisel. But be careful, it can get away from you in a hurry.  But its only metal and you can always weld her back up! 

  • Like 1

Kevin
1971 Mach 1

408C Stroker - C4 w/3,000 stall - 8.8" Rear w/3.73's - Disc brakes all way around.

 

 

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Cheers, the grinding of spot welds doesn't sound like a bad idea, specially coz you have to grind them down after drilling as well.

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Vinnie, feel free to go over my floor thread which goes into details and explanations of what to do and what not to do. But to answer your question, yes, you can do one panel at the time. Plan on taking twice as long as planned on the first half, and then half as long on the second half. One important aspect, expanding on what was said above, triple check before you cut. Other things you want to be aware of before cutting are wiring, brake lines, parking brake cable and most importantly the fuel line that runs along the driver's side. Since you will have to remove the parking brake bracket "hook" make sure you measure its location and try to save it if you want to reused it. The overlap welding with spot welds works very well. Just make sure you use weld though primer near the welds at the overlap so there is some protection there and then use some good seam sealer on both sides. My thread shows my technique which was derived from the many advises I received from members.

 

20160929_171923_edit2_small.jpg

 

1971 M-Code Mach 1 w/Ram Air, 408 stroker, 285/291 0.558" roller cam, Blue Thunder intake, TKO600, Hooker headers with electric cut-offs, FiTech EFI w/ RobBMC PowerSurge pump

Strange center section with Truetrac, 3.5 gear and 31 spline axles, 4-wheel disc brakes

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Good info here.

One thing that I would point out is that there are versions of the full length floor panels that have the bottom of the firewall/ toe board as part of the floor pan. If this is left on it makes the replacement obvious and gives it a non-factory look. If the bottom flange of the firewall/ toe board is damaged it makes the repair a little more complicated.

When I did mine I messed it up in the rear footwell because I wasn't paying attention to how flat or square the bottom of the footwell was to the rocker. If I were to do it again I would clamp a section of tubing or piece of wood across the bottom of the car so that you can set the rear footwell bottom at the same height, side-side. Mine is at the right height on the rocker side but slopes up as it goes across the car to the trans tunnel. It isn't obvious but once I noticed it I keep noticing it.It hasn't bothered me enough to fix it....yet....

Edited by mjlan
Clarity

Matt

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  • 2 weeks later...
13 hours ago, skerwath said:

Hotrod or vintage mustangs had an article on just this thing I read somewhere online.  I'll hunt for a link, unless you find it first.  http://www.onlymustangfords.com/floor-pan-replacement.html

Thanks! Some nice reading there. I'm still not sure how to do it since one side is still pretty good. Might replace one hole side and patch the other... We'll see :-)

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I bought both right and left side full panels and ended up only patching the rear foot wells. Still have the remainder of the panels if I ever need them. I did have to replace the panels under the rear seat as well as those are not part of the full side floors. Good luck, not a hard job, part of me wishes I would have just replaced the whole side when I did mine but in all actuality, I didn't need to. If you do a butt weld, it helps to have the little clamps that hold both panels in place. I got mine at Harbor Freight. Ended up not using them because I decided at the last minute to do a lap weld on top and underneath. Nothing wrong with that, just make sure you do top and bottom if you do a lap weld to  block any kind of moisture.  Good luck.

Tom

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7 hours ago, vintageman said:

I bought both right and left side full panels and ended up only patching the rear foot wells. Still have the remainder of the panels if I ever need them. I did have to replace the panels under the rear seat as well as those are not part of the full side floors. Good luck, not a hard job, part of me wishes I would have just replaced the whole side when I did mine but in all actuality, I didn't need to. If you do a butt weld, it helps to have the little clamps that hold both panels in place. I got mine at Harbor Freight. Ended up not using them because I decided at the last minute to do a lap weld on top and underneath. Nothing wrong with that, just make sure you do top and bottom if you do a lap weld to  block any kind of moisture.  Good luck.

Tom

Butt welding is all I have done with my trunk floor patches, quarter patch, drop off, wheel well and LH cowl. Those clamps are a MUST have, they help getting things spaced and level perfectly. On my LH side I really only need to replace a patch (lap welded...) in the rear but the RH side has holes in the front and another lap-welded patch in the rear. Having both complete sides replaced will look great but why remove metal that is still good? I'll decide when I get to it in a month I think...

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