Full floor pan install

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Nick Mailloux

Nick Mailloux

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Hey guys I just placed an order for a full floor for my swinger. What's the preferred method to install it? Ive never done a unit-body pan, only full framed cars and trucks. Do I leave it sitting on its own weight? Whats some thing to look out for?
 
Make a frame jig to keep everything in the correct location. There are engineering books available that have the dimensions.
 
Dana67Dart said:
Make a frame jig to keep everything in the correct location. There are engineering books available that have the dimensions.
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Now thats a lot of work. Im not even looking to strip the car down that much. Maybe pull the engine and trans, get it done quick and dirty. Im not looking to build a show car but would like it to be reasonably straight at the end. Seeing as how crooked they were from the factory, theres got to be a good easy way.
 
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4 cheap spirit levels. Jack the car and place Jack stands on rear framerails just forward of the rear shackles, and Jack stands on front framerails just forward of the K frame. Place one spirit level on each rocker with door sill plate removed, one across the trunk transition pan floor with trunk mat removed, and one across upper radiator support lip. Use my pix as a guide. Use thin aluminum or steel shim stock between Jack's and frame to get the front and rear level side to side, and car level front to back. Once jacked and leveled, do not move it until the new pan is in. I mean you can move it with the pan out, but then you have to go through the whole process with leveling and shimming to make the car square.

For changing the floor pan out, the way to make it easier besides pulling the engine and trans, is to also remove 1 door, and the steering column. Then you roll down the rear quarter window on the side you removed the door on, and the pan installs from that side. Fwd part facing down, rear part sliding in through the quarter window opening.

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moparmat2000 said:
4 cheap spirit levels. Jack the car and place Jack stands on rear framerails just forward of the rear shackles, and Jack stands on front framerails just forward of the K frame. Place one spirit level on each rocker with door sill plate removed, one across the trunk transition pan floor with trunk mat removed, and one across upper radiator support lip. Use my pix as a guide. Use thin aluminum or steel shim stock between Jack's and frame to get the front and rear level side to side, and car level front to back. Once jacked and leveled, do not move it until the new pan is in. I mean you can move it with the pan out, but then you have to go through the whole process with leveling and shimming to make the car square.

For changing the floor pan out, the way to make it easier besides pulling the engine and trans, is to also remove 1 door, and the steering column. Then you roll down the rear quarter window on the side you removed the door on, and the pan installs from that side. Fwd part facing down, rear part sliding in through the quarter window opening.

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Perfect! I think I may try it this way. I'm thinking if I pull the engine/trans and k-member, that will help prevent any distortions as well. Awesome, I was wondering what the best way to get the whole pan in would be, sounds surprisingly simple.
 
Ron816 said:
View attachment 1715711910 Put mine in Jack stands then just started cutting, not as involved as some let on.View attachment 1715711909

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Agree with this. Everyone thinks they need a damn frame rack and welded frame table to put a floor in. Like the car is just going to fold up under it's weight. Cut the damn floor out and weld it together. Depends on how bad your floor is but I'm going to guess there are holes on the inner rockers by the seal belt mounts. Inners are on sale now from amd for 42 bucks.

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67Dart440GT said:
Agree with this. Everyone thinks they need a damn frame rack and welded frame table to put a floor in. Like the car is just going to fold up under it's weight. Cut the damn floor out and weld it together. Depends on how bad your floor is but I'm going to guess there are holes on the inner rockers by the seal belt mounts. Inners are on sale now from amd for 42 bucks.

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Thank you ill probably pick some up. I figured it would be fine on some 12 inch wheel cradles. as long as my floor is good and flat. I might pull the engine and trans and kmember then just some good jack stands right?
 
I agree with not overthinking it to a point. It's not going to fold up, however here is that point. Concrete floors arent dead level. I had to shim 2 of my stands to get the empty car body dead level. If its not level when you install the pan, the induced twist in it will remain after its welded up. I have seen and fixed twist on full frame car chassis from people jacking up one side, and welding in bracing for a frame hitch. Then down jack the ***** and wonder why it drives crooked. I personally sawed out a C channel from a full framed GM car then had to un shim the upper control arms because they gave it a twist when they welded the C channel in then shimmed the living hell out of one side to make it drive straight.

These cars "WERE" assembled on level and square jigs on the assembly line. This kept the chassis square until everything that was going to be welded on, was welded on.

Dont believe me? Pop the plastic plugs in the trunk floor and transition pan that line up over the framerails and look straight down through them. The framerails have corresponding same sized holes in these locations. I'd venture a bet that these frame jigs had very specific diameter pins with a shoulders machined into each of them. The front and rear rails were set into them. The pans and pieces were set on the same pins to line them up, clamped down and welded. These jigs were also set up to build both the barracuda/duster 108" wheelbase chassis and the dart/scamp chassis which was I think 111". Yep the holes were left on the framerail side as drains, but that was not their initial purpose.
 
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moparmat2000 said:
I agree with not overthinking it to a point. It's not going to fold up, however here is that point. Concrete floors arent dead level. I had to shim 2 of my stands to get the empty car body dead level. If its not level when you install the pan, the induced twist in it will remain after its welded up. I have seen and fixed twist on full frame car chassis from people jacking up one side, and welding in bracing for a frame hitch. Then down jack the ***** and wonder why it drives crooked. I personally sawed out a C channel from a full framed GM car then had to un shim the upper control arms because they gave it a twist when they welded the C channel in then shimmed the living hell out of one side to make it drive straight.

These cars "WERE" assembled on level and square jigs on the assembly line. This kept the chassis square until everything that was going to be welded on, was welded on.

Dont believe me? Pop the plastic plugs in the trunk floor and transition pan that line up over the framerails and look straight down through them. The framerails have corresponding same sized holes in these locations. I'd venture a bet that these frame jigs had very specific diameter pins with a shoulders machined into each of them. The front and rear rails were set into them. The pans and pieces were set on the same pins to line them up, clamped down and welded. These jigs were also set up to build both the barracuda/duster 108" wheelbase chassis and the dart/scamp chassis which was I think 111". Yep the holes were left on the framerail side as drains, but that was not their initial purpose.
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This is all only relevant if the car twists. Measure to the floor on one side and the other, cut the pan out and measure it again. If it didn't move which it won't weld it in. Obviously supporting the car is required in high stress areas. Research a datum plane. Body men have been doing this for 50 years with no frame tables, leveling a car or any of the other saw it on TV crap.

Here is a lazer level stuck on a control point.with no floor, no inner rocker and it didn't move one mil.

Tape measures don't lie.

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I agree, tape measures dont lie, but if your concrete floor isnt level , and you cut the entire main floor pan your gonna have something that's not square. Its gonna want to move. I'm not gonna argue semantics with you. I level my **** with 4 spirit levels you can get at northern tool for about $3 each before I put pans in. You act like I'm talking rocket science. It's cheap insurance if your concrete floor isnt level. Do it how you want, it takes an extra 15 minutes to shim and level it once your stands are in place. Do you think you might want to ensure something is level and square when it's been pulled this far apart? Maybe before you start welding pans back in? This ain't my first rodeo either. See pix below.

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moparmat2000 said:
I agree, tape measures dont lie, but if your concrete floor isnt level your gonna have something that's not square. Its gonna twist. I'm not gonna argue semantics with you. I level my **** with 4 spirit levels before I put pans in. Do you think you might want to ensure something is level and square when it's been pulled this far apart before you start welding pans back in? This ain't my first rodeo either. See pix below.

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What is level going to tell you? You have a level car on an un-level surface? What is your datum plane then? An un level to the car floor?

Speaking of the pictures above. You have the entire rear frame rails hanging in the wind with absolutely no support whatsoever and are worried about it being "level"? I ask again. What is your datum plane when you are leveling a car to an unlevel floor?
 
67Dart440GT said:
What is level going to tell you? You have a level car on an un-level surface? What is your datum plane then? An un level to the car floor?

Speaking of the pictures above. You have the entire rear frame rails hanging in the wind with absolutely no support whatsoever and are worried about it being "level"? I ask again. What is your datum plane when you are leveling a car to an unlevel floor?
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I'm only replacing the front floor pan. The rest of my car isn't cut into absolute pieces either. I think that's gonna be a definite difference don't you think?
 
The first 2 pix I was getting ready to primer the whole *** end after sandblasting. I wasnt too concerned about that at the moment as I was not sticking sheetmetal back in yet. Additionally the framerails , tiebar, and rear valance were still attached together when I took those pix. I removed enough for sandblasting and left about a 1" strip the width of the trunk from the trunk floor tying it together for a moment. I removed that when I started on the trunk pan. Not sure what your talking about with the datum plane in regards to an automobile. I deal with specific datum in regards to aircraft. However if you use a level across the radiator support upper flange and across the transition pan that gets your car level side to side. If having to shim between the stands and the frame to get it level shows that your floor is not dead level. Its concrete. It will be close eyeballing it, but wont be perfect. Once you got the front and rear level side to side, then you put levels on the rockers, and shim and level it front to back. So far everything seems to line up for me. If rather be a little over cautious and double and triple check and not have to drill something back apart. Again I am saying do it how you want to, I will do it my way.
 
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Nick Mailloux said:
I'm only replacing the front floor pan. The rest of my car isn't cut into absolute pieces either. I think that's gonna be a definite difference don't you think?
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Sure it will be stiffer. Set a carpenter's level on your shop floor. See how flat or not that it is. Fancy laser level, or a couple cheap spirit levels still will prove out the same thing IMHO.
 
moparmat2000 said:
Sure it will be stiffer. Set a carpenter's level on your shop floor. See how flat or not that it is. Fancy laser level, or a couple cheap spirit levels still will prove out the same thing IMHO.
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I was planning on checking my floor with my 8 foot levels before beginning. I do agree there isn't anything wrong with being extra cautious.
 
BTW heres the pic of the old valance and trunk floor edge attached, , then the strip of floor I removed to start getting ready for the new trunk floor install

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If you have any prospect of installing subframe connectors, now is the time to do it - BEFORE you cut the old pan out. They go a long way to keeping the car from tweaking as you put the floor in. If you use USCT connectors that weld to the floor pan, you can install in the front and back at the subframes and then settle the new pan onto the connectors and weld them up as part of the process. Same goes for torque boxes since you are removing the pan above where they install.
 
str12-340 said:
If you have any prospect of installing subframe connectors, now is the time to do it - BEFORE you cut the old pan out. They go a long way to keeping the car from tweaking as you put the floor in. If you use USCT connectors that weld to the floor pan, you can install in the front and back at the subframes and then settle the new pan onto the connectors and weld them up as part of the process. Same goes for torque boxes since you are removing the pan above where they install.
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My cars already a hack job. The previous owner cut out portions of the floor and tech screwed and seam sealed individual sections. Scary right. This car is structurally unsound in the floor area and was driven like this before I bought it. I've also driven it this way. Should I still do frame connectors before attempting this repair?
 
It depends on what you want to do with the car in the long run. The connectors sure do stiffen the whole car - a lot less lean and twist. If you have your eye on a potent small block or a big block it's probably worth the time. I've always bought something pre-made, but lots of guys here swear by buying box tube and doing it themselves. If you use pretty big box tube you might need to cut a slot for it through the rear seat foot wells (what we do for race cars here), but the USCT ones are cut to fit to the floor pan and the floor pan becomes the 4th side of the box, just like chrysler did on the subframes.
 
str12-340 said:
It depends on what you want to do with the car in the long run. The connectors sure do stiffen the whole car - a lot less lean and twist. If you have your eye on a potent small block or a big block it's probably worth the time. I've always bought something pre-made, but lots of guys here swear by buying box tube and doing it themselves. If you use pretty big box tube you might need to cut a slot for it through the rear seat foot wells (what we do for race cars here), but the USCT ones are cut to fit to the floor pan and the floor pan becomes the 4th side of the box, just like chrysler did on the subframes.
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Potent small block in the future for sure. I just got a Dr diff 8 3/4 housing. Just ordered a front end rebuild kit from pst with torsion bars. I was just more concerned of doing subframe connectors first vs after the floor, because of how the car is already. I may do some form of subframe connectors first just to help keep it as straight as possible. I'm assuming just make sure the car is straight, and my doors open and close. Maybe take a bunch of measurements and weld em in right? Then floor from there?
 
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do you need a factory frame sheet to measure it out? If your swinger is a 70-71 I can scan one and send it to you...
If the car sagged in the past someone might have adjusted the doors to fit although that would leave gaps that were uneven somewhere (narrow to wide), right?
 
str12-340 said:
do you need a factory frame sheet to measure it out? If your swinger is a 70-71 I can scan one and send it to you...
If the car sagged in the past someone might have adjusted the doors to fit although that would leave gaps that were uneven somewhere (narrow to wide), right?
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It's definitely got some funny gaps but not necessarily to wide I don't think. Mines a 73. The drivers side door striker panel is booger welded too. I ordered that panel already. I'll look and see if I can notice any oddly shaped door gaps tomorrow after work.
 
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I just noticed that you are in Orting. I'm over on Vashon. If you want to see a set of USTC connectors in place you can come look at my cars.
 
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