Accelerator Cable for Dual Carbs ? Options

[cary]

In putting Mark's engine back in and replacing the broken accelerator cable. It seems the cable isn't quite long enough to work/fit correctly. In the FI arrangement the cable crosses the engine at 45 degrees. In dual carbs it needs to come at the bar at 90 degrees. Which pulls the bowden out of the firewall. Which will allow water down the cable tube.

What have others done to work around this ?

[Darren C]

Cary,
Sometimes you have to go with your gut feeling. The DD is a good but not fallible reference.
You need to consider several things in our 40+ year old cars.
Starting at front.
1, The gas pedal.
I’ve changed several of these over the years in my various 911’s and also in my 914 and got a whole new feel.
The metal hinges inside the pedal rust and go stiff so can affect the resistance and feel. The hinges can also wear and even break inside the rubber and you wouldn’t necessarily know. The pedal design also relies in part to the rubber moulded around the hinge to act as a natural return to the upright position when you let your foot off.
If you replace it, buy GENUINE Porsche, for a few dollars more you get a thicker steel inside and better quality hinge than the aftermarket copies.
2, Pedal set bushes.
If worn these will cause issues in smooth operation and increased friction.
3, Cable route at the pedal end and chassis tube.
It is possible to cross over the accelerator & clutch cables inadvertently when replacing them so one runs across another. You can’t see easily inside the tunnel and this can happen especially if the accelerator cable tube breaks free at the pedal end. Corrosion is an issue here as it causes friction and closes down on the cable if the tube is rusty.
4, Cable.
ALL cables wear. Most owners carryout a Carb conversion and use their old accelerator cable thinking it’s ok. Bowden cables wear the nylon sheath on the inside radius of any bend and the outside radius at each end of any bend and cable outlet from each end of a sheath. Over time if a cable is undisturbed you don’t really feel any difference as you get used to it and the change is so infinitely small. It only becomes an issue if the nylon sheath breaks somewhere (usually where the steel ferrule fits at the bulkhead) wears through, the cable sheds a wire or jams and the sheath external spring rusts out.
Cables also pick up dirt and dust and fray which can give resistance. I've had cables out of a car and they run free (making you think they're fine) refitted them and they bind under operational tension or when asked to lay in awkward routes.
The worst thing owners can do is oil these accelerator cables in good faith. This can swell the sheath, attract dust/dirt to quickly clog up and although you think you've solved an issue temporarily, long term its just made things worse.
The cable is a cheap item (in Porsche terms) and easy to replace, so if you're unsure how old your cable is and what condition it's in...just change it for peace of mind.

When owners carryout a FI to carb conversion, one big issue is moving an old cable around the engine bay to the new linkage mounting point. Just doing this itself can create a binding as the old worn cable is now bending/laying in a different position so any internal wear from where its “worn in and settled” over the years can be an issue
Cary, its difficult to have a good reference unless your reference is a car with all new parts down the chain. If you jumped in the car and thought “hey this pedal feels stiff” then 9 times out of 10 I’d say go with your gut feeling. Comparing it to an “unknown quantity” another DD is a starting point but certainly not to be relied upon.
Looking at it logically, on FI you have only one throttle body, one butterfly valve and 2 springs (dependent on year, there’s a coil on the shaft and a secondary emergency spring introduced a little later). On a carb conversion you have 2 spindle, 4 throttle butterflies, two coil springs, and additional springs that come with your linkage, and maybe more springs owners have added to get the throttles to return. Plus most linkages have friction points and odd mechanical advantages thrown into the equation.
It’s for this reason that I’d question your comparison with the DD against your gut feeling here.
If anything I'd say the DD with FI has an issue if its got the same heavy pedal feel/resistance as the carb conversion car!

Regards
Darren

[somd914]

If anything I'd say the DD with FI has an issue if its got the same heavy pedal feel/resistance as the carb conversion car!

I can say that I converted from D-Jet to dual carbs using the existing cable that was re-routed. My CSP linkage turned out to be somewhat lighter, better throttle feel, and returns faster in comparison to how the D-Jet was, though I'll admit this is a qualitative assesment as I didn't instrument the rig.

I'm not attempting to draw out an argument, just saying what my experience has been.