Firewall Flexing...looking for options - Vintage Mustang Forums
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post #1 of 17 (permalink) Old 08-03-2017, 09:58 PM Thread Starter
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Firewall Flexing...looking for options

I'm doing a t5 conversion in my '65 Mustang and went with the mustang Steve setup. I bought his firewall adjuster, fox booster, pedals with the quadrant, and the reinforcement plate for the firewall where the pedals mount to the firewall.

Everything is hooked up now. While I was adjusting the clutch cable I couldn't help but notice a horrible creaking noise and tons of firewall flex. See video below (copy and paste into the address bar if clicking the link doesn't work)

https://1drv.ms/v/s!Aq0rbhaiSGJ0gZEYbT8Nu-l9nenP4Q

Is this anything I should be concerned about? I'm worried that the firewall will crack over time. To be honest I'm quite upset that I invested as much as I did into this setup only to see so much flex in the firewall.

I'm not sure what to do right now and am looking for options. I could leave it as is and stop worrying about it. If I convert to a hydraulic clutch setup then I'll have the big hole in the firewall from the clutch adjuster and I'll need to convert to manual brakes because the hydraulic clutch setup doesn't fit with the booster there. If I convert to manual brakes I will then have the problem of my firewall being modified for the bolt pattern of the fox booster. I'd prefer not to run manual brakes if I can help it because I'm running Cobra disc brakes on all four corners.

Any thoughts or ideas on where I should go from here?

Corey
1965 Mustang Coupe
2001 Camaro z28
2006 300 SRT8
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post #2 of 17 (permalink) Old 08-03-2017, 10:16 PM
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post #3 of 17 (permalink) Old 08-03-2017, 10:35 PM Thread Starter
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Originally Posted by cla5675 View Post
It looks like that's for manual brakes only, yea? Or will it work with a brake booster?

Corey
1965 Mustang Coupe
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post #4 of 17 (permalink) Old 08-04-2017, 09:19 AM
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I don't think it'll clear the booster by the looks of it, but they might offer a different one. I actually added a flat plate behind mine too, came with the Ron Morris kit, lengthened the pushrod the same, and it works fine. Your video won't open, so not sure just how bad yours really is, but mine barely moves at all.

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post #5 of 17 (permalink) Old 08-04-2017, 09:54 AM
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Quote:
Originally Posted by 50 Proof View Post
It looks like that's for manual brakes only, yea? Or will it work with a brake booster?
Buy the parts from McMaster-Carr and fit it where you can.

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post #6 of 17 (permalink) Old 08-04-2017, 12:01 PM
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Have you contacted Mustang Steve about your concerns? Many, many of us have his products including the cable clutch conversion kit. Steve will surely be available to assist you. Hopefully, it is nothing that can't be resolved easily and inexpensively.

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post #7 of 17 (permalink) Old 08-04-2017, 12:30 PM
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I've read a few threads about firewall flex.

Is this an issue with hydraulic clutches too, or is it more of a cable clutch issue?

Dan
Chapel Hill, NC
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post #8 of 17 (permalink) Old 08-04-2017, 01:55 PM
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One of my earliest memories about driving an early 'Stang is how I could feel in my feet the floor and lower firewall flex when hitting standing water with any speed Not rotten just the way it was.
If you strip it apart I wonder if a doubling of the skin and panel bond or spot weld might be good?
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post #9 of 17 (permalink) Old 08-04-2017, 02:00 PM
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Quote:
Originally Posted by Dan Babb View Post
I've read a few threads about firewall flex.

Is this an issue with hydraulic clutches too, or is it more of a cable clutch issue?


I have a hydraulic clutch and feel some flex as well.

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post #10 of 17 (permalink) Old 08-05-2017, 02:06 AM Thread Starter
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I spoke to Mustang Steve and he advised that this is all normal. He mentioned even the original manual transmission mustangs with the linkage have firewall flex. Seems like this is nothing I should really worry about too much.

Corey
1965 Mustang Coupe
2001 Camaro z28
2006 300 SRT8
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post #11 of 17 (permalink) Old 08-05-2017, 08:27 AM
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WHen I put my hydraulic master in, I welded a small 1/8" plate with some gusseting (with two nuts welded to it) to the clutch/brake pedal housing so the master bolts directly to the housing sandwiching the firewall and therefore eliminating all flex. I didn't like the flex. I tend to over-engineer things as these types of projects are part of what I enjoy about this hobby, (winters are long here). The design is such that all the stresses never leave the housing...
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post #12 of 17 (permalink) Old 08-05-2017, 09:04 AM
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Originally Posted by dobrostang View Post
WHen I put my hydraulic master in, I welded a small 1/8" plate with some gusseting (with two nuts welded to it) to the clutch/brake pedal housing so the master bolts directly to the housing sandwiching the firewall and therefore eliminating all flex. I didn't like the flex. I tend to over-engineer things as these types of projects are part of what I enjoy about this hobby, (winters are long here). The design is such that all the stresses never leave the housing...
How big was the 1/8" plate? Do you have any photos of it, I have some 1/8" plate and a brand new throatless shear I want to use.

John

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post #13 of 17 (permalink) Old 08-05-2017, 09:29 AM
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Boy if you lived near me, this would cost you a beer - took a while to get decent shots... The gussetting looks like 1/8" but the plate looks thinner. I did this years ago so frankly I'm just happy I remembered I did it...

Cheers,

M
Attached Images
File Type: jpg Clutch master mount II - small.jpg (94.4 KB, 81 views)
File Type: jpg CLutch master mount -small.jpg (97.8 KB, 83 views)
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Last edited by dobrostang; 08-05-2017 at 09:32 AM.
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post #14 of 17 (permalink) Old 08-05-2017, 09:53 AM
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Originally Posted by dobrostang View Post
Boy if you lived near me, this would cost you a beer - took a while to get decent shots... The gussetting looks like 1/8" but the plate looks thinner. I did this years ago so frankly I'm just happy I remembered I did it...

Cheers,

M
Thanks, I owe you an adult beverage

John

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post #15 of 17 (permalink) Old 08-07-2017, 08:36 AM
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I agree that even new, there was a lot of firewall flex on most of them. I had one that had very solid firewall, and two speed wipers. Turn those wipers on high and you could feel it in your feet every time those wipers whipped past.
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