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GT40 Tech - Fueling, Electrics, & Engine Cooling Petrol, Electrons, & Water

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Old 12th June 2017, 12:09 PM   #1
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GTD throttle cable re-routing

Hi all,
I'd like to re-route the throttle cable on my car so that it comes over the front of the engine to the carb. Currently the cable runs down the right hand sill and up near the exhaust system to the carb. I'm hoping in doing this that I'll have a smoother action from a shorter cable and less heat! Would love to hear from someone who's given this a go, cheers, Dave
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Old 12th June 2017, 01:49 PM   #2
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Re: GTD throttle cable re-routing

That's how I did mine. The car has run without issues related to the throttle cable for many years. The key is to use the highest quality push pull cable you can find. Spare no expense on the cable.

I include a couple of pictures. You will note you will need to use a bell crank system to change direction of the motion.
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GTD throttle cable re-routing-hpim1499-jpg   GTD throttle cable re-routing-hpim1500-jpg   GTD throttle cable re-routing-1-16-03-3aa-jpg  
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Old 12th June 2017, 02:05 PM   #3
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Re: GTD throttle cable re-routing

Baum Iron has high quality US made Morse cables custom lengths and ends 800-228-9222 Rod
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Old 13th June 2017, 02:07 AM   #4
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Re: GTD throttle cable re-routing

Hi Howard, thanks for the reply and photos - looks a great set up. Did you have any issues with the cable turn out of the sill into the engine compartment - not sure how tight that radius might be. Also would it not be possible for the cable to pull directly on the throttle linkage at the bottom.....or am I missing something?!
Cheers, Dave
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Old 13th June 2017, 03:35 AM   #5
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Re: GTD throttle cable re-routing

Hi Dave,
Iíve routed mine actually inside the chassis tube that runs along the drivers sill and then is routed up the bulkhead. I set the pedal end up so it a direct straight pull on the cable. You want to run the largest bend radii possible to minimise any internal friction and protest the cable from the heat. The cable doesnít have to be anything special (although I would use a low friction liner) if you minimise the length and maximise the bend radii.
Rgds,
Andy
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Old 13th June 2017, 07:52 AM   #6
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Re: GTD throttle cable re-routing

Hi Andy, thanks for your response and piccie - nice engine bay! I'm actually running a Holley 650DP but I guess as far as the cable routing it makes no difference. As long as there is room to have a decent radius into the engine bay from the side sill then all should work.....hopefully!
Cheers, Dave
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Old 13th June 2017, 12:25 PM   #7
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Re: GTD throttle cable re-routing

David. If I remember correctly I did try the "direct route" and use the shorter arm of the carb linkage. I think I didn't like the heavy action and odd throw length that resulted from the lack of mechanical advantage the short arm provided. The bell crank method will let you fine tune the throttle "feel" with the bell crank arm ratio to your requirement.

The other thing is the radius of the cable turns required to use the "direct route". It is pretty close to the minimum radius standard for the cable I used. The first turn out of the side pod isn't the problem. It's the turn at the top back towards the carb that is the sharpest. And there are two fairly tight turns using the direct route and one big arc at the rear of the motor using the long route.

As in Andy's example the pull at the throttle peddle on my car is direct. I would avoid putting a 180 degree turn there as has been done elsewhere. That's just one more friction generating turn that can be avoided.

The last thing was the spring. The long arm gives you the most return spring strength for a given spring and I like the idea of a direct 180 degree pull against the cable action. The mounting points on my intake also required the location of the bell crank mount and spring anchor. Yours may be different and should be taken into account in your solution.

Use a old cable or a length of extension cord to measure the radius of the turns, map your route, and length.

As I said, this system has worked very well for a long time for me. I am sure there are others that work equally well also. What ever you settle on, go for maximum reliability, component strength, and least possible cable friction. As you can see mine is all rod ends and steel bell crank construction.

Last edited by Howard Jones; 13th June 2017 at 12:34 PM.
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Old 14th June 2017, 08:00 AM   #8
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Re: GTD throttle cable re-routing

David I was working on my car last night, cable comes in from the rear and has always been fine. If I routed it through the front it would at least be a challenge and might even need a bell crank at the engine as the bend radius would be too small.So, could be done but might need a bell crank.
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Old 14th June 2017, 10:16 AM   #9
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Re: GTD throttle cable re-routing

Hi Howard, thanks again for the detailed input. I get everything you say....mechanical advantage of using the long lever, the 'tunability' of this set up and return spring orientation, however something's puzzling me! from your photos it looks like your cable is following the 'direct route' from the front of the engine back towards the carb - do you not have a pretty tight radius here then? Apologies if being thick! Regards, Dave
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Old 14th June 2017, 10:26 AM   #10
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Re: GTD throttle cable re-routing

Hi Dave, thanks for your response. I agree that there's not a lot of room round the front of the engine and as you and Howard point out the cable turn at the front of the engine back towards the carb might be too tight.....possibly requiring a bell crank. I'm not overly keen on the current set up with the cable so near to the exhaust and thought this might be a solution....we shall see! Regards, Dave
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Old 14th June 2017, 12:14 PM   #11
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Re: GTD throttle cable re-routing

Ya, you're correct. I was trying to layout the pros and cons for both methods. Sorry if it wasn't clear. My fault.

The up the front (direct route) and then using the bell crank method to reverse the pull motion to be able to use the long arm on the carb is the method I settled on. The turn radius's are near minimum's but within the envelop and will be OK if you use a high quality cable.

If you do it my way it is really a hybrid direct/bell crank system. How's that for clarity! There are many ways to do this and most will work. IMHO the key to a satisfying feel will be the quality of the cable.

So I hope that helps. At least you have some options.

Here's my source for the cable I used on both my GT40 and SLC. They are very helpful. Ask for the green covered high quality low friction throttle cable. They are in California USA and I think they would ship internationally but you would have to ask. If not I would be willing to help. PM me if that's the way you want to go when you have settled on specs.

California Push-Pull Inc. Cable Specialists Based in Chico, Ca.

Last edited by Howard Jones; 14th June 2017 at 12:20 PM.
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Old 15th June 2017, 01:55 AM   #12
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Re: GTD throttle cable re-routing

Aha....got it! hybrid direct/bell crank system....you should patent that! As you say, lots of options to think about. Really appreciate all your help and will start mocking things up to decide which way to go. Thanks for the link to the cable co. will check it out. Cheers,Dave
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Old 2nd July 2017, 01:31 PM   #13
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Re: GTD throttle cable re-routing

You need a cable suitable for something like a Scania lorry. They are lined with heat resistant material that stays slippery even when subjected to extreme heat.
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