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Author Topic: Floor pan replacement question  (Read 1173 times)

737driver

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Floor pan replacement question
« on: November 19, 2019, 12:16:02 PM »
On my 72 I am kind of at a crossroad of decision making. After I cleaned up the floor pan I started noticing more rust areas in the floor pans. It seems that I have two ways of going about it. First option is to order a new floor pan and replace it as one piece. The floor pans come with and without bracing. I believe my braces underneath are good so I could go with the floor pan without braces. However the floor pan without braces does not include the mounting hooks for the rear seat (which means I would have to use the old ones).

The second option would be to repair the rusted out sections using patch panels. Of the six sections of the floor 5 would need replacement. They are not huge areas but areas that would have to be replaced.

So what I am trying to figure out is, what would be the best course of action. I am leaning toward replacing the entire floor as one piece, but just trying to weigh the options. Has anyone removed and replace the floor pan as one piece? The toe boards are in good shape, so I would just be replacing back to the seam where it meats the upper rear seat. If I did this, would it be advisable to replace the floor with new braces? Or use the existing braces and transfer the lower seat brackets onto a new floor pan without the braces. If I decide to go this route is there any specific order or way to do this? Is there any special tools or items that I would need?

The second option would be to buy the patch panels and replace the rusted areas one by one.

Right now I believe the amount of time it will take will be about the same for either option, and I believe I have most of the tools and equipment to do the job. Any advice or opinions would be appreciated.
Thanks,
Jim
1979 Trans Am- Heritage Brown -W72 (Pontiac 400) -4Speed-WS6
1972 LeMans Convertible
1977 Trans Am
1972 Firebird
1971 Firebird
1970 Firebird
1977 MGB  Roadster Convertible

roadking77

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Re: Floor pan replacement question
« Reply #1 on: November 19, 2019, 02:33:53 PM »
Jim, I have replaced patch panels only. I have a couple of small ones to do on my 79 soon but again they will be just a small patch. I had a neighbor that did Pontiac restorations and I saw him do a couple of full floors. They intimidated the heck out of me. He had a 2 post lift which I am sure made the job easier. He thought I was crazy for patching my floors saying that a full floor would have been much easier. I would think if the braces are good then leave them, but Im not sure how you would get the new floor pan in with them in place? I would almost think it needs to be installed from the bottom up. Also, need to make sure the body is braced pretty good as well.
I do know that putting them in as patches is pretty easy and straightforward.
Finished!
77 T/A - I will Call this one DONE!
79 TATA 4sp-Next Project?
79 TATA - Lost to Fire!
86 Grand Prix - Sold
85 T/A - Sold
85 Fiero - Sold
82 Firebird - Sold
'38-CZ 250
'39-BSA Gold Star
'49-Triumph 350
'52-Ariel Red Hunter
'66-BSA Lightning
'01-HD RoadKing

Jack

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Re: Floor pan replacement question
« Reply #2 on: November 19, 2019, 03:30:34 PM »
I've patched mine at few different places, I think a professional would do the entire thing but some one with less experience and resources typically only patches. I've seen people also revit the panels on (not that I would ever do anything like that).




Regards, Jack

roadking77

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Re: Floor pan replacement question
« Reply #3 on: November 19, 2019, 03:44:50 PM »
I have a buddy with a classic that the previous owner patched the floor boards with fiberglass. They are strong, and rust resistant! Not sure I would do it that way.
Finished!
77 T/A - I will Call this one DONE!
79 TATA 4sp-Next Project?
79 TATA - Lost to Fire!
86 Grand Prix - Sold
85 T/A - Sold
85 Fiero - Sold
82 Firebird - Sold
'38-CZ 250
'39-BSA Gold Star
'49-Triumph 350
'52-Ariel Red Hunter
'66-BSA Lightning
'01-HD RoadKing

FormTA

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Re: Floor pan replacement question
« Reply #4 on: November 19, 2019, 05:24:22 PM »
I have done the small patches and the large left and right ones. If I ever have to do it again I will do the whole thing without the braces.  It eliminates a tone of weld grinding.  Keeping you floor braces keeps everything in place and reduces fitment issues.

That's  my take on it.
79 Trans am low buck LS swapped
79 Formula 301 (Work in progress)
67 RS Camaro (This one is next)


Names, Luke. If I hear anyone telling me they're my father....

737driver

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Re: Floor pan replacement question
« Reply #5 on: November 20, 2019, 01:29:15 AM »
I wouldn’t mind doing patch panels, it would give me some welding time and experience. Recently I did get my hands on a rotisserie which might make that job a bit easier.

On the other hand the floor braces are in good shape from what I can tell, so if I replaced the entire floor I believe I would be able to do it with a floor without the bracing already built in.

I’ve searched TAC for threads on replacing the entire floor, and either the pictures are gone or blurrred by photobucket.

Either way it’s really a coin toss, the cost will be about the same either way. I certainly appreciate the input and advice from everyone .
Jim
1979 Trans Am- Heritage Brown -W72 (Pontiac 400) -4Speed-WS6
1972 LeMans Convertible
1977 Trans Am
1972 Firebird
1971 Firebird
1970 Firebird
1977 MGB  Roadster Convertible

737driver

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Re: Floor pan replacement question
« Reply #6 on: November 20, 2019, 01:44:57 AM »
I have done the small patches and the large left and right ones. If I ever have to do it again I will do the whole thing without the braces.  It eliminates a tone of weld grinding.  Keeping you floor braces keeps everything in place and reduces fitment issues.

That's  my take on it.

Just curious about how I would go about it, I take it that the original floor would have to be removed off the braces by removing the spot welds, then obviously on the front and rear seams. Then the old floor looks like it could be removed through the front windshield area.  From that point all the areas would have to be cleaned, prepped and primed for welding. Then ( I’m guessing here) the new floor would also be prepped for welding and then installed the reverse of removal , then welded back in similar to factory weld points. Then reattach console and rear seat brackets, and then apply seam sealer.
I’m not sure if I need to additionally add bracing to support the body while doing this and should remove the subframe as well.

Thanks for any advice or suggestions! :)
Jim
1979 Trans Am- Heritage Brown -W72 (Pontiac 400) -4Speed-WS6
1972 LeMans Convertible
1977 Trans Am
1972 Firebird
1971 Firebird
1970 Firebird
1977 MGB  Roadster Convertible

FormTA

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Re: Floor pan replacement question
« Reply #7 on: November 20, 2019, 05:58:16 AM »
Sounds like you have the basic plan there. I like to lay the new floor on top (after 95% of the old floor is removed) and cut through the new floor and the old with a cutoff wheel. Screew the new florence in place first. Then weld the seams.

I know it wouldn't be like the factory but that is how I think I would to the sides by the rockers unless they are rusted really bad. It's tough to get to that part where they were factory spot welded.

I would support the car a bit with whatever I had just to keep it in place. Cut as much out around the braces and the either trill out the spot welds or use a air hammer to rip the metal off of the support.

Sorry this is not in order.  I am in a hurry to get to work.
79 Trans am low buck LS swapped
79 Formula 301 (Work in progress)
67 RS Camaro (This one is next)


Names, Luke. If I hear anyone telling me they're my father....

roadking77

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Re: Floor pan replacement question
« Reply #8 on: November 20, 2019, 07:41:26 AM »
I didn't think about fitting it through the windshield, but if it fits that would be perfect. A full replacement would be the way to go. A whole lot less welding, resulting in a better looking finished product. I second what Luke said about an air chisel. If you dont have it, get one. I found it was much easier cutting the spot welds then drilling them out. Plus you wont end up with a zillion holes in your braces.
Finished!
77 T/A - I will Call this one DONE!
79 TATA 4sp-Next Project?
79 TATA - Lost to Fire!
86 Grand Prix - Sold
85 T/A - Sold
85 Fiero - Sold
82 Firebird - Sold
'38-CZ 250
'39-BSA Gold Star
'49-Triumph 350
'52-Ariel Red Hunter
'66-BSA Lightning
'01-HD RoadKing

FormTA

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Re: Floor pan replacement question
« Reply #9 on: November 20, 2019, 10:35:20 AM »
I like the spot weld cutters (which lets you only drill through one layer) but it's so time consuming and you can peel and rip a lot and chisel through most of it and then grind clean.
« Last Edit: November 20, 2019, 07:14:51 PM by FormTA »
79 Trans am low buck LS swapped
79 Formula 301 (Work in progress)
67 RS Camaro (This one is next)


Names, Luke. If I hear anyone telling me they're my father....

Doright

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Re: Floor pan replacement question
« Reply #10 on: November 20, 2019, 10:37:34 AM »
Jim
A full floor is NOT an easy task! and NOT to be taken lightly there are welds you cant get too or duplicate that the factory did!

You need to think about how the Uni-body was assembled at the factory!
They started with the Firewall and forward and rear floor sections adding the rear trunk pan then the cars sides then finally the roof.
Full Rockers upper and lowers where welded to the quarters with the trunk drop offs then attached to the previous welded floor sections (fire wall floors and trunk floor) then the rear seat divider is added rear tail panel installed before the roof is attached.

Because of the way they did it there will always be spot welds that can not be duplicated easily by the home hobbyist or basic body shop.
There is also the squareness of the build to consider and how to hold it and then checking it with Tram Gauges and other dimensional measurements that must be taken verified and adjusted if necessary to keep the body square. The Floor is a Major part of the Uni-body construction. 

A replacement panel IS NOT ORIGINAL!!!! it can never be called original once replaced! a repaired original panel is still a Original panel no matter how bad or how butchered it may be from the installer and it can always be re repaired!!!!! or replaced, A non original panel is still just that NOT ORIGINAL!

Having done some serious rust repair I feel I am more than qualified to advise you To REPAIR the floors DO NOT REPLACE! UNLESS they are flat out TOTALLY GONE! and even then WHY? Find another car to start with! sometimes its better left as a parts car. I am guilty of saving one or two that should have been scrapped so I know my 70 is a prime example. That said a well performed patch is undetectable when done correctly!

I invite you and encourage you to take a drive out here to my shop and look at my 70 on the spit now inspect it and my work up close and personal!!!!
Youll see the work I have done and see what you think needs to be done to yours.
I can show you places to look at and give you some pointers on what to expect and to watch out for and even let you try some welding both Mig and Tig and Gas if you like?  and offer advise on materials to use.

I also advise you to get the car fully stripped and fully inspected BEFORE you start on any of it and be prepared for the DAM I didn't see that one!!!!!
I just ran into one its not a major deal but its still yet another little something slowing me down that I have to deal with before I can proceed. 

There are many tricks and gotchas that are not included in my threads or by many others that have done this type of work at the level were talking about.
Pros are not gonna tell you or anyone else about all there Tricks or mistakes or the knowledge they gained from those mistakes they learned the hard way doing it!  Remember It really looks so easy on the internet after looking at a few pictures but remember this is how pros make money! they have learned the hard way and they know how to fix there mistakes! 

I am NOT a pro body man, collision repair specialist or Restoration expert nor am I ASE certified!
Dennis Barnett 
A&P Mechanic & FCC
Those who sacrifice liberty for security deserve neither!
B. Franklin

Doright

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Re: Floor pan replacement question
« Reply #11 on: November 20, 2019, 01:30:55 PM »
Check out this video skip to 14 min mark shows floor assembled first before rocker panels and quarters are attached and fitted
https://www.youtube.com/watch?v=bN1ChbUZDYQ

this one around the 21 min mark
https://www.youtube.com/watch?v=RAL5-B2ROkw

Also I have a set factory skinned full quarters hanging waiting for a car to put them on I can show you some of the welds I am talking about.
« Last Edit: November 20, 2019, 02:09:57 PM by Doright »
Dennis Barnett 
A&P Mechanic & FCC
Those who sacrifice liberty for security deserve neither!
B. Franklin

Ford5of5

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Re: Floor pan replacement question
« Reply #12 on: November 20, 2019, 06:19:02 PM »
I'm gonna agree with Doright with the exception that it might be worth the trouble to fix. 70-73 is getting hard to find without rot or at a price that's easy to afford.

You may want to consider buying a complete floor and cutting patches out of it. On my 79 it would have been more cost effective than buying 4 different panels and spring braces like I did. Also, chances are good that the spring braces could be shot. In regards to my 79, Doright is 100% correct; it should have been stripped as a parts car but that's also the reason why I wasn't afraid to attack it with an angle grinder and a mig. :shock: :lol:

737driver

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Re: Floor pan replacement question
« Reply #13 on: November 21, 2019, 02:45:26 AM »
Those are some great videos to watch! They make the assembly look easy.

Right now I’m going to do patch panels. I’ve thought about the areas I need to fix and assessed the work and find it do able. I will have it on a rotisserie soon so I think that will make the work more tolerable being able to work on it from different angles.

Jim
1979 Trans Am- Heritage Brown -W72 (Pontiac 400) -4Speed-WS6
1972 LeMans Convertible
1977 Trans Am
1972 Firebird
1971 Firebird
1970 Firebird
1977 MGB  Roadster Convertible

Doright

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Re: Floor pan replacement question
« Reply #14 on: November 21, 2019, 03:39:53 AM »
Jim
the Spit is a must have It will make job much easier i waited a long time for mine wish I had gotten one sooner worth every dime.

I also encourage you to mount it to the Pinch welds like I did BUT also encourage you to design the mount a little different than my current design I am going to redesign my Pinch weld carriage mount as soon as I am done with this car. again you should come out and talk or call me I am only an hour away in Pahrump.
Bring some beer!
Dennis Barnett 
A&P Mechanic & FCC
Those who sacrifice liberty for security deserve neither!
B. Franklin

Re: Floor pan replacement question
« Reply #14 on: November 21, 2019, 03:39:53 AM »


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737driver

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Re: Floor pan replacement question
« Reply #15 on: November 22, 2019, 02:52:46 AM »
Jim
the Spit is a must have It will make job much easier i waited a long time for mine wish I had gotten one sooner worth every dime.

I also encourage you to mount it to the Pinch welds like I did BUT also encourage you to design the mount a little different than my current design I am going to redesign my Pinch weld carriage mount as soon as I am done with this car. again you should come out and talk or call me I am only an hour away in Pahrump.
Bring some beer

Thanks for the advice , definitely would like to check out your project sometime!
Jim
1979 Trans Am- Heritage Brown -W72 (Pontiac 400) -4Speed-WS6
1972 LeMans Convertible
1977 Trans Am
1972 Firebird
1971 Firebird
1970 Firebird
1977 MGB  Roadster Convertible

Doright

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Re: Floor pan replacement question
« Reply #16 on: November 22, 2019, 07:28:22 AM »
Jim
I found a little project i would love to get my hands on

https://www.i-f-s.nl/wp-content/uploads/2018/08/901.jpg
Dennis Barnett 
A&P Mechanic & FCC
Those who sacrifice liberty for security deserve neither!
B. Franklin

Ford5of5

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Re: Floor pan replacement question
« Reply #17 on: November 22, 2019, 07:49:38 AM »
So the plane comes with new tires but does it have the 1970 model year specific missiles? Lol

I know nothing about aircraft but that does look like a really fun project. Needs racing stripes though.

FormTA

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Re: Floor pan replacement question
« Reply #18 on: November 22, 2019, 10:44:51 AM »
Humans didn't come with wings... I prefer to stay on the ground... If a ground machine loses power, it coasts to a stop. If air machine loses power, generally it crashes in a fiery ball.
79 Trans am low buck LS swapped
79 Formula 301 (Work in progress)
67 RS Camaro (This one is next)


Names, Luke. If I hear anyone telling me they're my father....

Ford5of5

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Re: Floor pan replacement question
« Reply #19 on: November 22, 2019, 01:01:39 PM »
I want to agree with you, Luke but I've seen cars go airborne 3 times in my life and once turn into a fiery ball while standing still. LOL! :lol: 6 of one and half a dozen of the other. :shock: Oh, and I'm not your father. I've had the same issues as my last name is Ford; every gym teacher I've ever had nicknamed me Henry.
« Last Edit: November 22, 2019, 01:03:32 PM by Ford5of5 »

737driver

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Re: Floor pan replacement question
« Reply #20 on: November 23, 2019, 02:28:46 AM »
I spend a lot of time flying all different kinds of planes. I can honestly say I feel safe in a plane. However I can understand the sentiment. I will say I have had more close calls in cars though.
:)
Jim
1979 Trans Am- Heritage Brown -W72 (Pontiac 400) -4Speed-WS6
1972 LeMans Convertible
1977 Trans Am
1972 Firebird
1971 Firebird
1970 Firebird
1977 MGB  Roadster Convertible

roadking77

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Re: Floor pan replacement question
« Reply #21 on: November 23, 2019, 07:53:59 AM »
Im with you Luke. I had an uncle who started flying during WW II, then was a commercial pilot for the rest of his life, dad always had a fascination with flying and my son shares the same passion. Im not afraid of flying, but will only do so when necessary.
Finished!
77 T/A - I will Call this one DONE!
79 TATA 4sp-Next Project?
79 TATA - Lost to Fire!
86 Grand Prix - Sold
85 T/A - Sold
85 Fiero - Sold
82 Firebird - Sold
'38-CZ 250
'39-BSA Gold Star
'49-Triumph 350
'52-Ariel Red Hunter
'66-BSA Lightning
'01-HD RoadKing

Doright

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Re: Floor pan replacement question
« Reply #22 on: November 26, 2019, 08:31:19 AM »
With enough cash I am sure I could make it fly again No problem their BUT

I was thinking more along the lines of scavenging the parts and engine from it and building a car out of it.
something like this:

http://www.gregwapling.com/hotrod/land-speed-racing-history/land-speed-racing-sonic-arrow.html

https://www.youtube.com/watch?v=tvdAw8dJ9cU

Now if I could just win the lottery
« Last Edit: November 26, 2019, 08:38:41 AM by Doright »
Dennis Barnett 
A&P Mechanic & FCC
Those who sacrifice liberty for security deserve neither!
B. Franklin

roadking77

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Re: Floor pan replacement question
« Reply #23 on: November 27, 2019, 08:28:16 AM »
Now that's just flat out crazy!!
Finished!
77 T/A - I will Call this one DONE!
79 TATA 4sp-Next Project?
79 TATA - Lost to Fire!
86 Grand Prix - Sold
85 T/A - Sold
85 Fiero - Sold
82 Firebird - Sold
'38-CZ 250
'39-BSA Gold Star
'49-Triumph 350
'52-Ariel Red Hunter
'66-BSA Lightning
'01-HD RoadKing

Re: Floor pan replacement question
« Reply #23 on: November 27, 2019, 08:28:16 AM »
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