Progressive throttle linkage

[BottleFed70]

Hi guys,

The throttle body I'm using is a little on the large side. With 5 speed manual and 3.73 rear gears it can make low speed throttle control a real pain. Parking lots suck as I can't seem to maintain a constant speed...

Since the throttle body I'm using is part of a TBI fuel injection unit, I can't swap it for a smaller model and don't really want to sacrifice top end performance anyway.

So what I'd like to do is figure out some way to install progressive throttle linkage. Meaning... the 1st 50% of pedal movement only opens up the throttle body to 25% open. The remaining 50% of pedal travel opens the throttle the remaing 75% until fully open.

Does anyone have any ideas on how to do this? The TBI throttle body unit i'm using has linkage exactly like a holley 4bbl carb. I have a welder and I'm not afraid to cut out the existing linkage if I can figure something out.

Any input would be appreciated.

[fury fan]

Visit some junkyards and look at some newer horizontally-mounted throttle bodies. Many of them have a cable that wraps around a 'guide' and opens the throttle. Sometimes the guide has a varying radius from the throttle shaft. Increasing the radius of the guide causes more distance (more pedal travel) for a given change of angle on the blades.

You might not be able to use parts like this, but it may give you an idea for somethign you can make. Maybe you could take your existing setup and re-weld it a little off-center from the existing throttle shaft???

[BottleFed70]

Visit some junkyards and look at some newer horizontally-mounted throttle bodies. Many of them have a cable that wraps around a 'guide' and opens the throttle. Sometimes the guide has a varying radius from the throttle shaft. Increasing the radius of the guide causes more distance (more pedal travel) for a given change of angle on the blades.

You might not be able to use parts like this, but it may give you an idea for somethign you can make. Maybe you could take your existing setup and re-weld it a little off-center from the existing throttle shaft???

Thanks for the info. I do plan to visit the junkyard.

I've also heard mention of a "snail linkage" which may be easier to fabricate.

[pluisje]

hi,

i went from 2x35mm SU carb's to 4x42mm Weber style throttle bodies.

you can imagine if you open 4x42mm on a 1500cc engine, you are opening very fast

anyway, with this system;

you open the throttle slowly at start and faster at the end.

or any leaver that is rotating, will rotate faster when the force-point is almost at the rotating point,
so you could mount a leaver between your pedal and the throttle body,
having the leaver rotating slowly at first, speeding up at the end..
does it make any sence?

[TT350chevelle]

Something with a changing radius should work, like an elliptical throttle plate. The cable must be attached to take advantage of the changing radius. I'll try to get me idea across with a pic.

Brad J.