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Old 23-10-2019   #1
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Repairing center heating tunnel

Hello again. Working on a 500F and noted significant rust damage to the center heating tunnel as well as the floor section that it covers. Before I start, is there anything I should be careful with when cutting into the tunnel?

I did remove all of the parts attached to it, as well as the all the cables, fuel line, etc. that run inside it.

Grateful for any advise; thank you!
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Old 23-10-2019   #2
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Re: Repairing center heating tunnel

That is a great question. I just re-did my interior carpeting and noticed a lot of dirt, dust, grime, some rust in the tunnel. Its too bad there isn't a way to remove it, without cutting it out. Or at least I didn't see a way.

If you have all the cables and fuel lines out, then I would think you are in great shape to dig right in and cut. I don't see anything else really attached to it.
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Old 23-10-2019   #3
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Re: Repairing center heating tunnel

Be aware that the central tunnel does contribute a fair bit to the car's stiffness. You must therefore make sure that you have added some bracing to the cars structure before you cut out the central tunnel
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Old 23-10-2019   #4
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Re: Repairing center heating tunnel

Thank you for the response. Yes, the previous owner used self-tapping screws and some sort of adhesive to hold down the carpet. I didn't notice this so when I pulled the carpet, it took pieces of the tunnel with it.

I wasn't aware that the tunnel was a structural element, but it makes sense. Now I'm worried that my car is misaligned. I was hoping I could get away with replacing it without any braces, but I guess I have bigger problems now!
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Old 24-10-2019   #5
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Re: Repairing center heating tunnel

Instead of removing the whole thing, can you strategically cut portions of it and weld in fresh pieces of metal? That way you preserve most of the integrity of the car.
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Old 25-10-2019   #6
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Re: Repairing center heating tunnel

I'm not really sure. I thought it might be easier to replace the whole thing instead of welding several smaller panels.

When I pulled the carpet, the section between the starter/choke lever and hand break broke apart. After I stripped everything, I used the air chisel and more of it started to come apart to the point where there was very little material left to hold up the starter/choke lever so I immediately stopped. The floor and the floor reinforcements looks to have been replaced recently, so I thought I could safely cut out what's left of the center tunnel, patch the area under it, and weld on the replacement tunnel.

I thought the rockers and the floor reinforcements would be able to take most of stresses, but I have never cut into a transmission tunnel on a unibody car and I'm FAR from an expert. I'm going to leave it alone for now and first figure out how I need to brace this. Always grateful for any advise/comment/etc...
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Last edited by myoshik; 25-10-2019 at 01:35.
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Old 25-10-2019   #7
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Re: Repairing center heating tunnel

Quote Originally Posted by myoshik View Post

I thought the rockers and the floor reinforcements would be able to take most of stresses, but I have never cut into a transmission tunnel on a unibody car and I'm FAR from an expert. I'm going to leave it alone for now and first figure out how I need to brace this. Always grateful for any advise/comment/etc...
Sean @Franko500 is the expert on this and even had a new one fabricated and then welded it in before they became commercially available.

I've dealt with some very rusty 500's so would be surprised to see an unsalvageable tunnel on a salvageable car, but I'm regularly being taught things.

The tunnel is definitely made from heavier steel than most other panels and relies less on pressings and more on this basic strength than the rest of the car. I would avoid removing it and patch in carefully as you go, as recommended by @tminus3. Someone with reasonable skills should find this quite straightforward and be able to do a good job of tidying the repairs. As a monocoque, in theory all parts are of equal importance to the stability of the shell, but I think that removing the tunnel without having the car fully supported on a jig would be a very unwise thing to do.

The floors can be removed completely, if you tackle one side at a time, and although this does cause some flexibility and obviously affects the stability of the shell, as long as the sills and tunnel are attached at both ends and are continuous despite being corroded) I find that if you take care and keep everything level, the car remains dimensionally stable.
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