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Muscletang needs new floor pans - advice?


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I knew there was a surprise waiting for me under the carpet. However, this is a bigger surprise than what I was expecting. With winter fully here I started my investigation of the "guts" of the car. I have not found rust anywhere except the floor pans and bottom of firewall as shown in pictures. When the car was restored they did what appears like a horrible job of repairing the floors. There is fiberglass on the floor over the pans. Off course, over time the rust continued and as you can see in the places where I removed the fiberglass there are areas where the pans are thin. I made most of the holes while poking with the screw driver. The rear floor panel on the driver's side is the only one that looks "solid," but I assume I am better off just replacing the full panels on both sides.

I have been reading the threads about how to repair and although it seems a lot of work, it looks very doable and reasonably priced. I am looking at this floor pans, http://www.cjponyparts.com/floor-pan-full-length-1971-1973/p/FLP4P/

Welding aside, is that all I need? These pans seem to have a little of firewall, but I don't know if I may need more due to the rust, thoughts? Also, how much of vertical wall do they have at the edge that meets the door frame? I am concerned on how much should I cut away.


Note fix of the seat mount threads on driver's side rear-left bolt.

Bottom pictures show a patch of fiberglass and a close-up of the panel where the seat connects. I was not able to read what it says.

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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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Mine had similar area's of rust and even worse on the passenger side(due to the fresh air intake rotting out). I ended up buying both sides full pans, then cut them up accordingly. I wanted to utilize what ever existing good metal that was there, but definitely wanted to cut out any cancer and area's of suspicion.

It was a job, drilling, spot welding, seaming, floating out, sealing, then spraying the sound coating, but well worth the effort.

For me, it was better to cut the rear pans in sections and use what I needed, then to use the one piece compete drivers pan/passenger side pan.

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I was wondering if i should skip the step of removing the seat base pan (name?). Is there a reliable way to inspection the pan underneath? As far i can see through the holes it looks good.

I dont want to go through all the work of drilling it out and then find out it is in good shape. Or is it simply nonsense? Since i am there i should replace as well.

 

1971 M-code Mach 1

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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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I was wondering if i should skip the step of removing the seat base pan (name?). Is there a reliable way to inspection the pan underneath? As far i can see through the holes it looks good.

I dont want to go through all the work of drilling it out and then find out it is in good shape. Or is it simply nonsense? Since i am there i should replace as well.

 

Definitely remove the seat risers - you'll probably find floorpan holes under them as well. Make sure you take out your fuel line too, or you're almost guaranteed to grind through it when chopping out the driver's side pan.

 

This might be an ideal job to use 3M 8115 panel adhesive to adhere the panels at the overlap/lap joints. You could probably use it on the pans too, but the spot weld holes will look ugly if not filled up with weld.

 

-Kurt

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These are the pans I first looked at, http://www.cjponyparts.com/floor-pan-full-length-1971-1973/p/FLP4P/

but they also have the Dynacorn's, http://www.cjponyparts.com/dynacorn-full-length-floor-pan-coupe-fastback-1971-1973/p/FLP5P/

The later are $30 more. Any experience with either? CJ's offer expires today so I would like to order today.

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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:dodgy:go ahead with the floors, just make sure the inner and outer rockers are fine . if those are rotten you need to them first and they are tricky. Mach 5

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These are the pans I first looked at, http://www.cjponyparts.com/floor-pan-full-length-1971-1973/p/FLP4P/

but they also have the Dynacorn's, http://www.cjponyparts.com/dynacorn-full-length-floor-pan-coupe-fastback-1971-1973/p/FLP5P/

The later are $30 more. Any experience with either? CJ's offer expires today so I would like to order today.

 

I went with CJ's also. They weren't exact in all of the stamped patterns, but the shape was right on. When it's all said and done, know one will ever know, or even recognize the difference.

You can always give it a good whack with a metal hammer and listen to the sound. If it sounds dull, good clue that it needs to be replaced. Old school metal worker habit....

#DontMachMe making the rounds and being abused all the way

 

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Current stable- Ford Parking Only

1972 Mach 1 Mustang

1969 Bronco Sport

1964 Falcon 

2002 F250 4x4 w/ tuned 7.3 diesel

2015 Fusion Ecoboost Hybrid

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I guess that if I needed a little bit more metal on the firewall I could use any piece of straight panel beyond the floor pan edge.


This might be an ideal job to use 3M 8115 panel adhesive to adhere the panels at the overlap/lap joints. You could probably use it on the pans too, but the spot weld holes will look ugly if not filled up with weld.

 

Kurt, if I understand your comment, are you implying to adhesive bond all the panels rather than welding them? I was under the impression that the panels had to be welded to the subframe square tube running underneath. Is it safe to bond the rest rather than weld? I assume you don't refer to bond the seat riser since I guess it has to be welded due to safety. Can you pleas expand? Thank you.

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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These are the pans I first looked at, http://www.cjponyparts.com/floor-pan-full-length-1971-1973/p/FLP4P/

but they also have the Dynacorn's, http://www.cjponyparts.com/dynacorn-full-length-floor-pan-coupe-fastback-1971-1973/p/FLP5P/

The later are $30 more. Any experience with either? CJ's offer expires today so I would like to order today.

 

Likely the same tooling. The cost difference makes it a no-brainer; go with Dynacorn so you don't have to worry/return substandard pans.

 

-Kurt

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How to buy a '71-73 Mustang:

Rule #1: Assume all classic car sellers are guilty until proven innocent.

Rule #2: No classic car dealer is ever innocent; thus, they are all guilty.

Rule #3: Buy from trustworthy people: Fellow forum members. Visit 7173Mustang's For Sale forum.

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:dodgy:go ahead with the floors, just make sure the inner and outer rockers are fine . if those are rotten you need to them first and they are tricky. Mach 5

The outer rockers sound and look good. The passenger side seems to have been involved in some type of accident at some point. Look in the picture at how the top of the rockers appears chopped and the inner isn't straight. Because the top is not there I can inspect the interior of the rocker. It was dirty, but no rust.

The driver's side has the top and then some tape over it (bottom picture). I removed the tape since it appears a leftover from when it was painted.

Now I have a question about the passenger side rocker. Is that top piece missing a problem? should something be welded there or it doesn't matter?

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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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I have a bunch of vids that will help you with your floor pans...Do not use panel adhesive to replace the floor pans. UNLESS it's just a small hole your repairing.

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LOVE OF BEAUTY IS TASTE..THE CREATION OF BEAUTY IS ART

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I used the CJ floor pans and they seemed a bit thin to me. Dynacorn may be a bit thicker, but I dont know that for sure. Don from OMS would probably know if there is a gauge thickness difference. I like the adhesive but not on structural pieces. Welding should be done on the floor pans, pretty important piece to the unibody structure. You may consider lap welding the floor pan, its going to be easier than butt welding, but if you want to hide the joint completely from judges or whatever then butt welding maybe your thing its just a bit harder. I butt welded mine with a tig welder but its just because i wanted the challenge. Tig weld joints MUST be tight, Mig weld joints have a small gap to add the wire/filler material so they are a bit more forgiving. I was showing my 18 year old son some tig welding techniques so I thought the floor pan was a great place for him to learn. He is already an accomplished MIG welder. Don't forget to spray some type of coating inside the frame rails and rocker panels. If you weld the floor onto the inside of the rocker panel and do it right you will penetrate with your weld all the way through to the inside and melt any coating that may be "inside" the rocker panel, if there is any in there at all. This will be an unpleasant surprise to anyone who has welded the floor pans to the rocker and in a few years. Eastwood makes an inner frame coating with a 24" hose to get into the hidden areas. Good luck and keep posting Dennis

Dennis

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If your floor pans are rusted out, chances are your cowl(s) are as well. Make sure you inspect those!

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I have a bunch of vids that will help you with your floor pans...Do not use panel adhesive to replace the floor pans. UNLESS it's just a small hole your repairing.

 

Question Q: If nothing else, is it feasible to use the panel adhesive on the area where the pans meet the rockers, as opposed to the rest?

 

Just curious where the hazard factors in here.

 

-Kurt

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How to buy a '71-73 Mustang:

Rule #1: Assume all classic car sellers are guilty until proven innocent.

Rule #2: No classic car dealer is ever innocent; thus, they are all guilty.

Rule #3: Buy from trustworthy people: Fellow forum members. Visit 7173Mustang's For Sale forum.

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As cudaK888 said in a previous post, remove your fuel lines before you start cutting out floor pans. I'd suggest removing the fuel tank. too, before starting down that road. Also have a big fire extinguisher, or better yet, two, nearby. You don't want to catch your car on fire in the garage. It's a huge, expensive mess. Don't ask me how I know. :(

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Ron

Rusty, a 1973 Mach 1, needs a lot of work.

Billy, a 1976 Ford Bronco, also needs a lot of work.

El Guapo, a 1986 F150, frame-off Resto-Mod.

Bubba, my 1994 F150, daily driver

Formerly, a 1973 Ford Mustang Coupe - a work in progress, then a car-b-qued banana.

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Kurt, I believe the whole floor should be welded, even along the rockers, just because the amount of flex you can get.

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Just a thought.... what about adhesive all around and then spot weld around instead of a continuous bead. However, the heat may damage the adhesive. I have no experience in this field; just trying to stir thoughts.

 

1971 M-code Mach 1

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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I guess I am adding a welder to my Christmas gift wishlist.

I hear good things from Eastwood's M135: http://www.eastwood.com/mig-welder-110vac-135a-output.html

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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I guess I am adding a welder to my Christmas gift wishlist.

I hear good things from Eastwood's M135: http://www.eastwood.com/mig-welder-110vac-135a-output.html

 

Make sure you weld the pan in. DONT use adhesive, the floor is a major structural part of the car. If you don't mind seeing the seam, make it easy on yourself and overlap the seams. I butt welded mine and you cant even tell its there, but its time consuming and pretty challenging if you have never welded before. Buy a good spot weld cutter and some bits for it. Also get a cheap flanger/punch tool from harbor freight so you don't have to drill 100 holes by hand! http://www.harborfreight.com/air-punch-flange-tool-1110.html

Watch Q's videos and you will be fine. Its pretty straight forward and easy.

As far as your welder goes, I have had very good luck with my eastwood 175 mig welder. I would recommend the 220volt if you have access to 220 in your garage. Burns in better and can be used for many other jobs if need be. If your just doing small sheetmetal jobs the 110 volt mig 135 will be fine. DONT used shielded welding wire. Its a mess. dirty welds that don't look real pretty. Spend the extra cash and buy a bottle of 75/25 co2/argon mix and use solid wire. Burns much nicer and cleaner.

Take your time and inch up on your final cut. Don't try to get it all in one piece. AS said before remove your fuel line in that area. Take your time and enjoy learning a new skill!!!

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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Question Q: If nothing else, is it feasible to use the panel adhesive on the area where the pans meet the rockers, as opposed to the rest?

 

Just curious where the hazard factors in here.

 

-Kurt

No adhesive what so ever especially at the rocker as others have said it's a structural piece integral part of the unibody. The only place you could use would be a small patch to a existing good floor.

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Make sure you weld the pan in. DONT use adhesive, the floor is a major structural part of the car. If you don't mind seeing the seam, make it easy on yourself and overlap the seams. I butt welded mine and you cant even tell its there, but its time consuming and pretty challenging if you have never welded before. Buy a good spot weld cutter and some bits for it. Also get a cheap flanger/punch tool from harbor freight so you don't have to drill 100 holes by hand! http://www.harborfreight.com/air-punch-flange-tool-1110.html

Good tip about the butt weld bits. Didn't know them. I found this Blair set in Amazon: http://www.amazon.com/gp/product/B002XML5HK/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A1UMBRA5ZTBCX8 Are those good?

I don't have a big enough air compressor to run air tools. Forgive my lack of knowledge, what are the holes you talk about for? I am planing on going the lap joint weld route.

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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I have an Eastwood 135 and it has done very well for me. If you have 220V, then the 175 would be even better. But for sheet metal, the 110V welder works very well. And definitely use gas. Flux core totally sucks, and is even worse with sheet metal. As far as the spotweld cutter, the Blair 11096 has a 1/8" pilot bit, so will leave a small hole. The Blair 11082 would be a better bet. Check out http://www.autobodynow.com/collections/blair/products/blair-equipment-spotweld-cutter-kits-11082.

 

Good luck.

Ron

Rusty, a 1973 Mach 1, needs a lot of work.

Billy, a 1976 Ford Bronco, also needs a lot of work.

El Guapo, a 1986 F150, frame-off Resto-Mod.

Bubba, my 1994 F150, daily driver

Formerly, a 1973 Ford Mustang Coupe - a work in progress, then a car-b-qued banana.

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Now I have a question about the passenger side rocker. Is that top piece missing a problem? should something be welded there or it doesn't matter?

 

Really strange that it should be chopped up like that (makes me think of The French Connection!), as the rocker itself doesn't appear damaged anywhere except the inside, and a hit on the outside that would have done the same to the inside would have been nasty enough that the rocker wouldn't look like that today - nor the car.

 

Perhaps this was a parts car at one time, and that panel was cut out of it as a donor?

 

Here is the same area on a '73 rocker:

 

30xj5f9.jpg

 

No adhesive what so ever especially at the rocker as others have said it's a structural piece integral part of the unibody. The only place you could use would be a small patch to a existing good floor.

 

Makes sense - though why is 8115 touted to have a stronger tensile strength than steel?

 

Would it be unacceptable if someone looking for a beer-budget workaround were to plug weld most of the panel, but use a combination of plug welds and 8115 on a lap joint at the trans tunnel?

 

I'm not necessarily advocating lapping the panels, but for someone who wishes to do so, it would seem as if using the 8115 and plug welds would be a long-lasting method to seal the lap joint (provided it's epoxy to epoxy). Unless 8115 is particularly flammable...

 

-Kurt

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How to buy a '71-73 Mustang:

Rule #1: Assume all classic car sellers are guilty until proven innocent.

Rule #2: No classic car dealer is ever innocent; thus, they are all guilty.

Rule #3: Buy from trustworthy people: Fellow forum members. Visit 7173Mustang's For Sale forum.

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Really strange that it should be chopped up like that (makes me think of The French Connection!), as the rocker itself doesn't appear damaged anywhere except the inside, and a hit on the outside that would have done the same to the inside would have been nasty enough that the rocker wouldn't look like that today - nor the car.

 

Perhaps this was a parts car at one time, and that panel was cut out of it as a donor?

Good points. Then it doesn't make sense. Could it be that they cut it to check for damage or rust? But if so, why cut it so much.

I thought of an accident because that door doesn't close as easy, but that could also be some misalignment of the hinges or lock.


Makes sense - though why is 8115 touted to have a stronger tensile strength than steel?

The epoxy has a high tensile strength, but the assembly will be weakest at the epoxy-panel interphase, which will make the whole joint weaker. Maybe that's the issue.

 

Would it be unacceptable if someone looking for a beer-budget workaround were to plug weld most of the panel, but use a combination of plug welds and 8115 on a lap joint at the trans tunnel?

 

I'm not necessarily advocating lapping the panels, but for someone who wishes to do so, it would seem as if using the 8115 and plug welds would be a long-lasting method to seal the lap joint (provided it's epoxy to epoxy). Unless 8115 is particularly flammable...

If I were to lap weld all around, what should I use to seal the lap joint? Some kind of silicone or similar?


As far as the spotweld cutter, the Blair 11096 has a 1/8" pilot bit, so will leave a small hole. The Blair 11082 would be a better bet. Check out http://www.autobodynow.com/collections/blair/products/blair-equipment-spotweld-cutter-kits-11082.

Good luck.

Thanks found the Blair 11082 in Amazon.


A friend has a Hobart 140 welder. He hardly use it, so he will let me borrow it for a few weeks. I will practice and do the job with his then I can save some money to get one for myself. I spent too much purchasing parts this weekend.

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 points. Then it doesn't make sense. Could it be that they cut it to check for damage or rust? But if so, why cut it so much.

I thought of an accident because that door doesn't close as easy, but that could also be some misalignment of the hinges or lock.

 

How are your door gaps?

 

As far as the spotweld cutter, the Blair 11096 has a 1/8" pilot bit, so will leave a small hole. The Blair 11082 would be a better bet. Check out http://www.autobodynow.com/collections/blair/products/blair-equipment-spotweld-cutter-kits-11082.

Good luck.

Thanks found the Blair 11082 in Amazon.


A friend has a Hobart 140 welder. He hardly use it, so he will let me borrow it for a few weeks. I will practice and do the job with his then I can save some money to get one for myself. I spent too much purchasing parts this weekend.

 

+1 for both the Blair 11082 and Hobart 140 MIG welder. I used the same cutters on the spotwelds of my car - AND the same welder to put it back together. You'll love the Hobart; it's nicer than the comparable Lincoln 110's.

 

-Kurt

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How to buy a '71-73 Mustang:

Rule #1: Assume all classic car sellers are guilty until proven innocent.

Rule #2: No classic car dealer is ever innocent; thus, they are all guilty.

Rule #3: Buy from trustworthy people: Fellow forum members. Visit 7173Mustang's For Sale forum.

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