Narrowing rear seat

78 Mach1

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Feb 17, 2022
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German Valley, Illinois
I’m sure this is a rare modification I am doing. But thought posting it could help someone else if they were crazy enough to do it. Most people delete the rear seat when mini tubbing their cars. Especially since the MII rear seat is useless for anyone over the age of 12 anyway. But I am trying to keep my interior as close to factory looking as possible even with the tubs and large meats on the back. So I have decided to narrow the already tiny rear seat to fit in between my tubs. I also wanted to keep the factory option to fold the seat down. This is a current on going project. So I’ll post as progress moves along. Here’s what I’ve done up this point.

Original width from tub to tub is 41” with the seat back being 40”. I have 36.5” tub to tub and there for need my seat back 35.5” to retain the .5” clearance on each side. I have to remove 4.5” out of the seat back and the metal brace that folds down. I started with the metal seat back. I didn’t want to lose any structural support. So instead of cutting the 4.5” out of the center where there’s a main support. I decided to cut 2.25” out of the middle of each side. You can see my cut lines in the first picture. This allowed me to keep the main center structure support. Second picture shows them cut. Then I stitch welded them back together. It seems every bit as strong as before. I’ll be cleaning up the welds and painting next. But honestly this will all be covered up by the seat itself and the carpet. I’ll be doing the fold down bracket next. I believe the hardest part of this whole thing will be the upholstery itself. I’m nervous of how that will turn out.
 

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78 Mach1

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Here’s a visual as to why I have to narrow the back seat. I fabricated my wheel tubs and frame rails to move each tire in 4”. This allows me to fit a 12” wide Weld wheel with 28”x12”x15” tire. The first picture shows the frame rails moved in. The second two pictures show the cars current progress. You can see how much each wheel tub comes in past the original factory panels. That’s how much I have to narrow the rear seat to clear each tub. I love the factory interior on these cars and didn’t want to lose that look. Deleting the back seat would have been much easier. But not an option for me. And losing the fold down function was out of the question. I’ve always loved that about the MII fastbacks.
 

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78 Mach1

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I did the necessary modifications to the hinged metal brace portion today. There were no structural concerns on this piece. So I was able to just cut 4.5” out of the center. First thing I did was mark center and make my cut lines 4.5” apart. Then remove the hinge rod. It just pulled out.
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Then I made my cuts. It worked out perfectly that my two cuts fell in between two of the hinge fingers.
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I just pipe clamped it back together and stitch welded it.

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I purposely did not grind the welds flush because I felt leaving some meet at the seem gave it more strength. Plus everything you will see on final assembly will be covered by carpeting. Here’s with it done except final coat of black paint. I won’t do that until I get the mounting holes drilled in the car and everything fitted for final assembly.
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Up to this point. The hardest part was keeping the hinge lined up and working smoothly. Which I was able to do. I’m still nervous about the upholstery part. But we’ll cross that bridge when we get there. I’m no sewing expert. Besides drilling a couple mounting holes. That’s the next step.
 
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78 Mach1

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German Valley, Illinois
So I took yesterday off from this project. We had the nicest day in a long time here in Northern Illinois. I decided to pull the Cobra II out of storage. That was supposed to be a quick connect battery and drive. It ended up being a charge the battery, drain the tank, replace fuel filter, and rebuild the carburetor, adjust timing, and then drive. It’s never easy for me.

I got the mechanical back seat sections installed in the car today. It was a bit tricky getting everything lined up so it functioned smoothly. But I was able to do it. Keep in mind, I had to drill all new mounting holes because the old ones were cut out when the tubs were put in. I’m very pleased with how it turned out so far. I tried to attach a video of the seat folding down. File was to large. So you’ll just have to take my word that it works great. I obviously still need to paint and trim some of the carpeting. I’ll do that with the upholstery work.
 

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78 Mach1

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Interesting that you mention the panels. I had a real internal struggle with cutting the panels to fit around the wheel tubs. Mine were damn near perfect condition. Cutting them up was not ideal. I had no choice unless I just carpeted the sides. But I love the almost factory look I ended up with. I guess it was worth it in the end.
 
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extra_stout

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Most people delete the rear seat when mini tubbing their cars. Especially since the MII rear seat is useless for anyone over the age of 12 anyway. But I am trying to keep my interior as close to factory looking as possible even with the tubs and large meats on the back. So I have decided to narrow the already tiny rear seat to fit in between my tubs. I also wanted to keep the factory option to fold the seat down.
Awesome work. Very nice idea.
I like the fold down seats very much on this car. Also that you have a flat level. It is just very usefull and you still you have a mustang.
 

78 Mach1

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Feb 17, 2022
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German Valley, Illinois
I started on the upholstered seat portion today. This is much more involved and requires a lot more explanation than the previous steps. There for I am going to break it down in parts to prevent such long posts. Plus it’s going to take several days. Where the mechanical sections were a couple hours project.

First thing I did was is get a measurement of the original seat width for reference.
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As you can see, my rear seat upholstery is shot. It sat in storage for 15 years. I think a critter tried to eat it or something. I also want to note that the vinyl is very dried out and brittle as you can see in the pictures. I have conditioned it many times but is not helping much. What you may not be able to see in the pictures is just how cheap of a material this particular cover is made of. It is my belief that these seats were redone at some point. And whoever did them used the cheapest material they could buy at the time. My 76 Cobra II has the factory vinyl still in it. And those seats are much thicker/better quality material than what’s in this car. Again, I don’t believe this is factory vinyl.

My next step is to mark reference points of where the seat cover lines up with the seat backing board.
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Your probably asking why I marked these locations if I’m not reusing the original seat cover. The answer is, I am reusing it. Only for proof of concept. Keep in mind, I’ve never done anything like this before. If I mess it up, I’d rather mess up this old nasty seat cover instead of a brand new one. If I can cut the old one to work. Then I’ll risk doing it to a brand new one.

Next step is to remove the actual seat cover. This is easy. It’s only stapled to tue backing board. But there are some hidden staples going up the middle of each side and across the top. Once you remove the obvious staples along back edges. Then you fold the seat cover back and access the hidden staples.
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I also removed the foam. But no explanation necessary. It literally just pulls off.

Next step is to layout the necessary cuts to narrow the backing board. This also involves relocating a few relief holes for the bolts that go to the metal folding parts. I carefully measured and marked the new locations and cut lines. In my case, this was 2.25” in on both sides
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Then it’s just a matter of cutting and drilling new holes.
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You can see the lower dangling pieces now no longer line up with the outer edges. I just simply had to move them in 2.25”. I already cut the inner edges 2.25” to ensure clearance for the drive shaft tunnel. I had options with these and decided to do the full cut on them from the inside instead of the outer edge. Cutting the outer edge would have done away with the thicker foam on the outer edge. Since I’m going for a more factory look. I wanted to keep that bolstered outer edge. So I simply cut the inner edge of each and then relocated them 2.25” in so the line up with the rest of the seat back.
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The seat backing board is now done. Next will be cutting the foam. By the way. I do not want to end up with the same cheap material when it’s time to do the final reupholstery of all the seats. So if anyone knows of a good source for seat covers for this car pleases let me know. I have found Classic Auto Reproductions and Stock Interiors both carry them. Does anyone have any experience with either of these companies seat covers? Are they good quality? I’m fine with factory, but what I currently have is much thinner and cheaper than factory. Please give me any recommendations if you know where to get the good stuff. Thanks.
 
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LILCBRA

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As much as I'm a proponent of DIY, I'd end up taking it to someone to upholster. I have a set of covers that I got from Mustangs Unlimited before they went defunct. I don't know if they're made by the same company or even if it's the same material anymore since I've had them for a while, but they seem to be pretty decent. I mean it's not rich Corinthian leather or anything.... :shrug: :rlaugh:
 

78 Mach1

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Feb 17, 2022
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German Valley, Illinois
If I can’t make my old crappy cover look correct. I’ll do exactly that. Let a Pro do it. But I have to try. It’s no loss if I mess up this one. It’s toast anyway.

I’m sure your material is better than what I have. I’m not looking for Ferrari quality leather. Just something as good as factory vinyl. If you went to JoAnns Fabrics and bought there cheapest vinyl material they have, that’s what my seat upholstery feels like. Even the areas that are still ply able feel very thin and cheap. Just like what you get on a cheap set of kitchen chairs. I think these were maybe replaced in the 80s for the minimum money possible. Mine feel nothing like the factory vinyl that’s in my Cobra. I’m looking for something like what my Cobra seats are.
 
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78 Mach1

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Just got back from a local upholstery shop. They quoted me $1500 just to do the rear seat. Then an additional $750 for each front bucket seat to match. Looks like I’ll be doing this myself no matter how it turns out. There’s no way I’m putting $3000 seats in this car. I’d wrap the seats in bed sheets first.
 
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78 Mach1

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Feb 17, 2022
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German Valley, Illinois
I got the foam cut and replied back together. Just measured and cut 4.5” out of the center. Then used some of my left over glue from doing the headliner to glue the foam back together.
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Nothing left to do now except Frankenstein the upholstery to fit.
 
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78 Mach1

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Finally got around to doing the upholstery. Here’s the original cover.
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I first measured it then cut 2.25” out of each side.
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Next I sewed it back together. I’m obviously not good at sewing. I literally just learned how to use a sewing machine by watching a YouTube video minutes before sewing this seat. I used my daughter machine which is designed for clothes, not upholstery. You can see where I miss aligned the seams.

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This was supposed to be practice for when I get my new seat covers. But I decided to try and repair it myself as well. So I ordered some fake leather material from Amazon and patch the damaged areas.
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I feel it turned out decent enough to try it out. So I stretched it back over the seat foam and backing.
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Satisfied with it so far. I went ahead and mounted it in the car.
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It actually turned out way better than I ever thought I could do myself. So I have decided to keep it this way and not spend the money on new upholstery just yet. This project cost me $20 in material and around $10 in needles and thread. I broke three needles in this process because the equipment I was using is not made for this thick material. I feel it was definitely worth the time and minimal cost.

I’m actually thinking about borrowing my mothers better machine and trying to do the front seats in real leather. She has a nice machine that can handle the thicker materials. We’ll see if I decide to do that or not.

Still need to do the rear seat lowers. But those will be much easier than the back was.
 
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LILCBRA

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