I am re-assembling the '74 and decided to put my Tangerine SS fuel line in while the car is apart. I pulled the old line out - pushed the new one in and decided to go to the front access cover in the tunnel to guide it into place. I reached in - felt something moving that wasn't the fuel line. It is a broken clutch tube. I was thinking - terrific - I broke it pulling the old line out - but no. The clutch cable was run outside of the broken tube by someone previous to me and has been working that way since I have owned the car for about 10 years. It has just been rattling around in the tunnel.

Has anyone ever heard of this? I plan to repair the tube and correct the problem but it blew my mind.

Thanks!

Yup: I knew two cars that removed that tube and they swore it solved that entire mess...

Hey Jim,

I must say after driving it for many years I never noticed anything was amiss. Kind of makes me wonder...

See you soon!

.......Kansas 914, it will work....you just lost the *Guide*

It seems like it shouldn't work. Unless there's something else going on, like the cable goes into the tube further in the tunnel.

--DD

Tube is broken at both ends and is actually rolling around in the tunnel. On further inspection there appears to be some "custom" work on the rear firewall where the tube would have been.

The tube is welded to help with a weak firewall. It also guides it to the correct location up front. If the firewall has been stiffened and you have a solid chassis, I see no reason why it would not work perfectly. The fulcrum point it at the firewall as pressure is applied.

Thanks Mike - that makes sense and it does work well.

not one of porsches greatest design moments,a braided steel cable running through a steel tube that isn't straight..
The end result takes no guessing
Our handbrakes work through Bowden cables why did they not go that way.

Here is what mine looked before and after the repair also the tube in the tunnel was secured with a clamp/no welding..Before the clutch was releasing near the floor now just at the right spot and way easier to shift..
914 Click to view attachment Click to view attachment

Well Done!

The old repair looks like a brake hose clip.

If your firewall is strong enough the tubing to the front isn't really necessary
550 Spyders had the exposed clutch cable run 'as the crow flies' across the drivers floor pan !

Thanks! It makes sense now - but still weird when I first saw it.

My cars in the shop for a clutch tube repair. I'm thinking of having the tube removed. Is this going to come out easily,???

@Kansas 914

Nope.

See my build thread if you want details of how it's held in but it is brazed at the rear bulkhead, brazed into a tube pack that includes the heater cable guide tubes, and brazed at the front.

OK; how does the initial Kansas 914 post strike you ? Why can’t the tube in the tunnel be eliminated? Curioius.

The purpose of the tube is to stop forward movement of the cable housing, and to keep the cable working perpendicular to the firewall forward. Without that, there's nothing to resist or control the cable's forward movement.

In many cases, the tube is removed/falls off and the cable housing is stopped by the firewall itself. That's fine, it works, but now the cable housing is working against an open hole, plus it's not set perpendicular to the firewall. It will move around, flex the firewall, and the firewall will eventually fatigue crack; the cable housing will pop forward through that bigger hole, causing the cable to suddenly go slack.

Theoretically, if you could remove enough slack from the cable you could remove the cable housing entirely! But now the cable is rubbing along the edges of the firewall hole, down to the engine mount hole (assuming you're routing through it) and then back up to the forward edge of the housing mount where it goes through before going through the pulley. Now it's acting like a little bandsaw, sawing away at everything it touches each time you use the clutch. No bueno.

So can you remove the firewall tube? Sure. But the job of the firewall tube is to shorten the cable housing routing for better cable adjustment, focus the pull direction to perpendicular to the firewall, and to reinforce the firewall so it doesn't crack. If you do remove the tube and do not reinforce the firewall then it's a clock ticking until the firewall cracks and fails.

Honestly, I fail to understand why this is even controversial. It's really a simple process to re-weld/braze a new tube in place.

And it's the best design option.

Great explanation ! Thanks

The clutch tube also helps to keep the accelerator cable away from the clutch cable. If the two become intertwined, then shifting can cause the engine to rev a lot when the clutch is out. Quite the opposite of what you want to happen. Many who have replaced one or both cables have been quite surprised when the engine revs to redline when they put the foot on the clutch pedal. Normally it is a very good idea to have a solid clutch cable guide tube, and also reinforce the firewall. Heavy duty clutches put additional strain on the firewall.

How much difference would a 6 spring clutch be to the 4 spring ?

This is is my firewall before my temporary clutch tube fix. I will reinforce the firewall and attach the clutch tube to the reinforced firewall when I get into my new shop and have my welder up and running.

Click to view attachment

This is the temporary fix. It keeps the clutch cable sleeve from pulling into the firewall.

Click to view attachment

Jim, repair the weld. Where did it separate, Front, middle or rear?

If you do a hydraulic conversion you'll be done with the clutch cable problems forever

I did the conversion on the 'BB' and have the components to do the conversion on 'HOWARD' (after it get's straightened out)

Click to view attachment

Click to view attachment


Check with David ( @dwillouby ) to see if he still sells the brackets ...http://www.914world.com/bbs2/index.php?showtopic=324027&hl=

That is on my short list.. I would love to do this.

I think it will be hard to beat the OEM simple cable system with respect to weight.

I value 2000lb cars or better yet, even lighter.

Add:
master cylinder
Associated brackets
Slave cylinder
Reinforcement to pedal box
Hydraulic line
Weight of fluid
More fasteners at master & slave cylinder

Delete
Clutch cable & housing
Current light weight plastic pulley & OEM steel bracket
Maybe delete clutch cable tube if you can remove it while redoing floorpan or by hacking up the tunnel.

I have a feeling it's a significant weight add to go to a hydraulic clutch. Would love to see the actual weights involved.

The original engineers were pretty crafty to deliver a 2000lb car.

Cars still up on the rack. Shop hasn’t started in on it.

Hydraulic actuation is a good idea when you have a funky routing, such as Japanese cars (looking at you, Honda and Mazda) where the drivetrain was designed for right-hand-drive and modified for a left-hand-drive market.

But you can't beat the simplicity and longevity of a cable.

One can argue that the routing of the reverse-mounted 901 makes it worth the effort, but given these things lasted for half a century I'd find it hard to justify on a stock car.

Not opposed to the concept, mind you, but it just seems easier to buy a new cable and weld up the firewall every 50 years or so...

Springs in the clutch disc make engagement smoother but really have no affect on the cable.

Previous repair at the firewall around 2016