Throttle Solution

[Keep it stiff]

I'm have a problem with one of my cars and I can't figure out the solution.

With the throttle flat to the floor the cable is pulled by about 40mm. At the carb I need about 70mm of cable movement to fully open. I can't reposition the pedal. What I need is a solution that converts the 40 at one end to 70 at the other.

Any ideas?

[harrycovert]

You need to think about a lever ,small movement one end large movement the other, any way you can replicate that in your system extending arms,bellcranks etc?

[Doofus]

For bicycle brakes, you can get something called a Travel Agent (eg: https://www.sjscycles.co.uk/cables/travel-agent-br... ) which multiplies the cable pull.

[Gary C]

bell crank kit.

What's the carb ?

[Keep it stiff]

Thanks for the speedy replies. The lever idea is not one I had considered and I can see how would work. I will have a look to see what is available. There is reasonable space around the carb. The gadget designed for bikes, working on the cam principle, also looks interesting.

[Keep it stiff]

Gary C said:

bell crank kit.

What's the carb ?

It is a Holley on a small block, I think the cable mechanism is designed around a truck which no doubt has considerably longer pedal movement.

[OutInTheShed]

You need a buzzer:
https://www.pistonheads.com/gassing/topic.asp?h=0&...
:-)
you can probably find parts from another carb or throttle body to convert the cable pull you have to the throttle movement you need.

But ome sort of bell crank affair is an option.
Some multi cylinder bikes have various mechanisms to convert one cable to multiple butterfly movements etc.
Can be handy for a change of direction as well.

Or you could modify the pedal mech to pull more string.

[Ambleton]

You'll need to custom make something to get the exact ratio you need.

Bell crank or a lever arm would be easiest i would have thought. Can you change the arm/lever playe on the carb to reduce the throw you need?

[9xxNick]

As others have said, a bell crank would probably be a reasonably easy solution to engineer.

Based on experience though, it is very much worth your while to arrange the whole throttle cable assembly so that there's as little friction as possible in it, and absolutely nothing that flexes under load - your ability to "dial in" specific amounts of throttle and therefore power depend on this. In particular, I would avoid multiple 90 degree bends in bowden cable like the plague.

[V10Mike]

Keep it stiff said:

It is a Holley on a small block, I think the cable mechanism is designed around a truck which no doubt has considerably longer pedal movement.

If it’s like every other Holley I’ve seen there are multiple cable mounting positions on the bell crank, you just have to pick one nearer the pivot that gives you the movement you need. If not, there are aftermarket cable mounting solutions available.

[Keep it stiff]

A bell crank it is then, thanks for the replies. I can see various options on ebay, I will buy a couple and have a go, this should keep me entertained for hours!