Removing firewall (MK3.1 front d/s footbox) flex from clutch actuation

[efnfast]

I noticed that I have a lot of firewall flex when I clutch in (MK3.1, cable operated, big hp clutch) - after 15yrs of driving I guess it's okay since nothing bent from it, but probably best if I stiffen up the firewall.

If I bolt a 1/2'' aluminum plate behind the firewall (to the firewall) should that stiffen it up? Or will it inadventently create some type of lever effect that causes my firewall flex to become exacerbated and thus maybe result in bending the firewall?

Obviously the best solution would be to weld in a brace behind the firewall, but it's pretty damn difficult to work in there in a completed car, so I think it has to be a bolt-in solution.

edit: for clarity by firewall I mean the ?1/4''? steel plate that the master cylinder is bolted to and that the clutch cable hosing bracket (or clutch quadrant if using adjustable quadrant) attaches to ... I guess you could also call it the front plate of the footbox

[NiceGuyEddie]

Friend:

When you say "firewall" do you mean the large curved piece of aluminum that goes all the way left-to-right, or do you mean the piece of aluminum that's on front of the thick steel plate on the footbox?

[David Hodgkins]

Sakes alive, he lives!

Nice to see you again Alex.

The firewall is the piece between the footboxes. The clutch cable exits the driver's footbox. Is the driver's footbox what you are talking about? There is already a steel plate behind to .040 aluminum. Perhaps to are seeing the aluminum deflect? Do you have a pic?



EDIT: Eddie beat me to it!

[NiceGuyEddie]

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Yes, like David said, I'd be surprised if anything was flexing on the front footbox part. It's possible the aluminum "cover" on front of the footbox is covered a bit by the adjuster and it's flexing a bit. My cover isn't perfectly flat and flush against the metal plate. It's doubtful the steel plate behind it is moving.

[efnfast]

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Yes, like David said, I'd be surprised if anything was flexing on the front footbox part. It's possible the aluminum "cover" on front of the footbox is covered a bit by the adjuster and it's flexing a bit. My cover isn't perfectly flat and flush against the metal plate. It's doubtful the steel plate behind it is moving.

By firewall I mean the ?1/4''? steel plate that the master cylinder is bolted to and that the clutch cable hosing bracket (or clutch quadrant if using adjustable quadrant) attaches to ... I guess you could also call it the front plate of the footbox

The top edge of the ?1/4'?' steel plate (Where the clutch cable housing mounts into) is definitely flexing forward as the clutch actuates - i'm running a big horsepower clutch and it's pretty damn stiff

[David Hodgkins]

OK so I think we're in sync on the area you are talking about. Thanks for the pic Eddie!

Here's my .02: If MY clutch was so stiff that it is flexing that steel adjuster ring and/or steel, I'd convert to a properly sized hydraulic setup from Mike Forte. Yeah, it's most likely a body-off project. But hey, You've had that body off before. On the plus side, no more massive effort to clutch! Your driving pleasure will increase tremendously.

Best of luck with whatever solution you come up with, and it's nice to see you around again. Did you finish the SLC? post a pic!

[AC Bill]

Is the clutch really that heavy?
Sure it's not the cable binding, or perhaps the pedal box bushings are damaged, causing friction when the clutch pedal shaft turns?

[efnfast]

it's a single disk clutch meant for like 700hp .... it's not going to be light, lol.

I got my solution ... I hope.

I bolted a 1/2'' aluminum plate onto the back of the d/s footbox. The corner closest to the engine is obviously an issue because there's no way to secure it to the footbox since the clutch holding hole just sits in the middle of nowhere there. So I drilled/tapped the side of my 1/2'' aluminum plate, and then ran an adjustable rod end from the plate to the frame on the car.

I'll be the first to admit it's not the most elegant solution, but it should stop the top of the footbox from flexing from clutch actuation.

[efnfast]

OK so I think we're in sync on the area you are talking about. Thanks for the pic Eddie!

Here's my .02: If MY clutch was so stiff that it is flexing that steel adjuster ring and/or steel, I'd convert to a properly sized hydraulic setup from Mike Forte. Yeah, it's most likely a body-off project. But hey, You've had that body off before. On the plus side, no more massive effort to clutch! Your driving pleasure will increase tremendously.

Best of luck with whatever solution you come up with, and it's nice to see you around again. Did you finish the SLC? post a pic!

Finished the SLC almost a decade ago. And a 917. And 962. And a bunch of other stuff.

[CraigS]

Ya beat me to it. I was going to suggest a rod from one of the MC mount bolts forward to 'something'. Nice work on the reinforcement piece.