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Discussion Starter · #1 ·
Once again another infamous case of cracked firewall on my 86 gt. The car has a t5 in it with a dual hook steeda quadrant, and steeda adjustable cable. The car has 17k miles on complete new drivetrain. I went with a spec stage 3 clutch and it has always had a very firm pedal , but has not been that hard to get into gear. Recently It has been getting hard to get into gear, so I've adjusted the clutch several times, and moved the cable to the second hook on the quadrant. It gets better for a day or 2 and right back at square one. I got looking around today under the hood and I now have a crack about 2.5 inches long spreading towards the passenger side from where the cable mounts into the firewall. I had someone push the pedal from inside the vehicle while I examined the cable and the firewall flexes quite a bit when pressed. I also noticed the protective jacket on the cable is cracked down towards the adjustable end at the transmission. Do any of you guys know if there is a manufacturer of a firewall support for this issue, or am I going to have to buy some sheet metal and fabricate my own bracket to repair this problem? If I have to buy sheet metal how thick would you recommend? Or can I just weld the crack in the firewall and let it ride? I do plan on replacing the cable as well. I do however drive the vehicle everyday..
 

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This was a porblem in the f150's. They offer a support, however you should be able to pull the clutch items and have a thicker piece of metal welded in.
 

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Discussion Starter · #3 ·
I've been reading about it online spd.. I saw a good bit on the f150's but not much on fox's I think im going to call ford and see if they offer a plate to weld in. I welded up some of it as well as i could , but it definitely needs a reinforcement. I have seen a few mustangs do this but not crack like this one. Mine cracked all the way over to where the throttle cable comes thru the firewall.. once i get this issue taken care of I am going to go to a stage 1 or something streetable.
 

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Discussion Starter · #5 ·
I'm really considering getting rid of the car itself. I drove it to work today and it did ok. I went to get in it and go home and it wouldnt go in gear at all. I let off the pedal and bam the cable popped thru the firewall . Now i have a broken firewall, a car that cant be driven and a $10,000 investment that as just as good as scrap metal. I'm tellin ya man my luck ran out years ago haha.
 

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Discussion Starter · #6 ·
We have a confirmed fix for this infamous issue. I took a piece of 16 gauge sheet metal and cut it 3x3 (inches) Measured over 3/4 of an inch to the right and up approximately 1 inch and marked a hole and drilled an 1''1/4 hole for the new cable to pass thru, then marked a hole for the cable to bolt down to and drilled a #19 hole for the sheet metal screw to hold the cable in place. I drilled a 1/4 inch hole in all four corners and used 1/4 inch by 1'' self tapping screws to hold it in place. I hammered out all the cracks to be flush and bolted everything down. Went with a new summit cable and its like a completely different car. Firewall flex is gone. My old cable was cracked all the way up and was actually broken in half.
 

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My 79 Cobra had this issue after I installed a Zoom competition clutch.
The springs were too powerful for the stock cable set up.
Lesson I; For any modifications, all parts of the modified system must be comparably durable, or the system Will Fail.
Lesson II; A fresh stock clutch assembly will probably work fine, if you've built that much power that you need stage 3 equipment, you should read lesson I.
 

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Discussion Starter · #8 ·
Yea i have a spec stage 3 clutch , ford racing quadrant, ford racing cable.. but not much you can do for a for a firewall to support it but make a brace. I never had an issue until the cable broke through the jacket. The cable is what cracked the firewall. Im making 302 rwhp and 373 rwtq on 5psi @ 4500 rpms. Im making 450 rwhp on 12 psi and getting 16 mpg if i keep my foot out of it with the ac on .
 

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quick question on same problem

Hi, been cruising through forums and found plenty of people talking about it, but you were one of the first that had a solution. I know it has been a while since this thread has been active, but if you don't mind me asking, how has your fix held up, and might you be able to post a picture or two of exactly how you did it. Any help would be greatly appreciated!!!

-Keith
 

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I had this problem in my car back in the 90's and did something similar.
I wanted to spread the load out over as much area as possible so I used a pretty thick aluminum plate that covered that whole section of the firewall. I had it butt up against the bottom of the cowl seam and cut it out around the brake booster, etc.
I started with a cardboard template and then transferred it to the aluminum. Finished it off with a nice polish so it actually looked pretty trick. Wish I had a picture...
 
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