Throttle challenges

[mcrysdale]

I recently purchased Superformance GT40 P2282. I've have some throttle problems.

1) The end of the throttle cable snapped off. I don't claim to be a master mechanic (far from it). I spliced a new end on until I find someone more competent to replace the cable.

2) I was out for a drive and the pedal hit the floor again. I thought my splice failed, but when I checked it was fine. Turns out the bolt connecting the adjustable rod from the pedal to the piece that rotates and pulls the throttle cable had fallen out (what no Loctite?). I managed to get the bolt back in (by some miracle head first one handed under the dash with zero tools)...see next issue..

3) After reconnecting the throttle, next the throttle return spring failed (could would only rev up, not down). I macgyvered a wire pull on it to get home and shorten the spring. It sort of worked.

4) I felt compelled to dissect it and Loctite all the bolt in there so I want unpleasantly stranded again. I come to find out the rod connecting the pedal to the piece that pulls the throttle (sort still don't know what it's called) has ball joints to swivel with the swooping pedal action were mostly seized up and didn't move. I cleaned and lubed them best I could and reassembled everything. The pedal movement was so stiff the Throttle return spring was not up the job.

I would love to hear people experiences with their throttle/petal and any advise. Pictures would also help a lot (I think I have a missing nut on the break petal, but that's a smaller problem).

Thanks!

 

[Morten]

Speedy Cables will sort you a new cable

 

[Ian Clark]

Hi Matt,

Pictures at the pedal box and carburetor would be helpful, maybe the root cause of the failures can be identified.

There a many ways to bind or stretch a throttle cable, resulting in loss of WOT (wide open throttle) breaking of cable, bending associated linkage parts and worst case a stuck open throttle.

Shouldn't be too hard to figure out and make right.

Cheers
Ian

 

[mcrysdale]

I have since discovered my on the 'road' repair I attached the Petal to Throttle piece upside down (on the top rather than the bottom). That was why is was binding so bad! Disclaimer: I did fix this by feel one handed only under the dash in 80 degree weather on the side of the road with no tools. It's a miracle I connected anything at all I have since debugged/corrected that and the action is much better. The throttle return spring is still not up to the job (mostly but didn't get the idle all the way down), so I shortened the spring it a bit and it's working acceptably now.

I still think the throttle cable takes too many sharp turns, the connecting rods and the throttle return spring should be replaced. For now the car is functioning. I'm going to go interview a mechanic to see if I can find someone familiar with these cars to fix it correctly. Always a good idea to have a professional you trust for when you have bigger problems.

I will try and post photos for the next person when I can...

 

[Ian Anderson]

I always carried a few rubber bands in my car for these emergencies……amazing how they can be used to aid pedal return and also carb shutting.

 

[Mike Pass]

I always carry a spare throttle cable inner and several solderless nipples. If the cable snaps your local parts shop won't have a cable that long. Just pull the broken cable out and feed through the new one and fit the solderless screw on nipples. Make sure the ends of the spare cable are not frayed so they will feed easily. I solder the very tip of the cable so it won't fray.
Cheers
Mike

 

[mcrysdale]

The throttle return spring still isn't up to the job. I think the rod bearing swivels are too seized. I'm going to see about buying a new rod and spring(s) (or 2 to double it up if needed). I'll attach some pictures this time. The spring was stretched out like that before all this, yes I know it attached in the wrong location. I think they didn't put the right length spring on. The blue wire is my backup wire to pull if the spring fails

g

g on it.

 

[DaveM]

If the spherical bearings are binding by all means replace them. What spring arrangement do you have at the engine?

 

[Randy V]

I’m pretty certain that you can quite easily loosen up the Spherical bearings (balls) with just a bit of metal polishing compound or perhaps some valve grinding compound. You can put a small bolt through the bearing with a nut on the other side of the bearing. Chuck the bolt up in an electric drill. Rotate the ball to be able to push the compound into the socket, now hold onto the rod end or chuck it in a vice. Slowly turn on the drill to make the ball rotate inside the rod end. This will polish a small amount of material from the rod end’s socket - thereby loosening its grip on the ball.

 

[Ian Clark]

It's really difficult to see from a few pictures what's going on, although you do have to start somewhere. You may be in a geometric bind between the throttle pedal and the bell crank that pulls the throttle cable. The throttle cable may be faulty, kinked or unwound internally. The spring is definitely toast and destined to fail based on it's pull angle and range of travel. Also the rod ends or pushrod have issues.

You can narrow down the culprits by unhooking the throttle cable from the engine and the pedal box. That will reveal any or all of the initial concerns.

The throttle pedal and cable should be smooth and throughout their range of travel. The problem could also have begun at the engine end of the system, hence the suggestion to disconnect both ends.

You're probably in deeper than a new spring and adjusting rod ends. SPF did a fine job of reproducing the original pedal box and it's functionality, it's not working right so some component(s) may have failed on their own or helped by improper adjustment and setup.

Be prepared to pull everything out if you can't get to the bottom of it with the pedal box in the car. Been there, done that, no t-shirt to show for it but a lot of time upside down in the footwells of GT40 replicas of most types over the years.

Looking forward to what you discover, the eventual fix will give you a reliable and easy to modulate throttle.

Cheers
Ian

 

[Walter]

I'd say there are three items to be ckecked for free play individually: the throttle pedal linkage, the linkage at the intake, and the cable. In my case heat from the engine fried the cable. It got stuck after a cool-down. I replaced it by pulling the new cable in when pulling the old one out. Then I used a heat wrap to protect it.

 

[mcrysdale]

Update: I've replace the spring and recreated a new rod linkage from petal to throttle cable piece. I learned some when making the rod. I re-used the center threaded piece and what I screwed on the ends I just put a couple of screw drivers down the bearing hole and twisted (WRONG). BY the time I have them all the way threaded down, the bearing weren't running as smooth. Apparently you can damage the bearing or housing it spins in and it won't spin so good anymore. I get some more new ones and made sure to tighten them with a wrench (Duh, there is a reason they have a spot for a wrench).

 

[mcrysdale]

 

[Frank Catt]

See attached throttle pedal assembly

 

[Rick Muck- Mark IV]

View attachment 129898

Also ensure your cable is secured to the tub where it runs from the pedal assembly down the sponson. My first GT40 had the cable flopping around and caused a "too sharp" bend. You can use tape or cable tie anchors to locate the cable.

 

[Randy V]

Also ensure your cable is secured to the tub where it runs from the pedal assembly down the sponson. My first GT40 had the cable flopping around and caused a "too sharp" bend. You can use tape or cable tie anchors to locate the cable.

Good point Rick!
any movement of the cable jacket results in lost motion of the cable itself..