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FMX / Kickdown return spring?
#1
Okay,
I am working on my throttle linkage and FMX kick down.

Intake is an Edelbrock Performer RPM airgap, with an older Barry Grant Demon carburetor (before they got bought out).  Kickdown rod is a stainless unit made by kickdownrods.  I have the rod tweaked to perform as instructed by Kickdownrods.

Now I am looking for ideas on the kickdown return spring, and throttle return spring...

I know this is a touchy subject because it is 100% critical for safety and not experiencing an unexpected WOT situation.

Anybody have any good ideas and or photos?

Thanks,
Peter
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#2
I'm not familiar with your setup and it actually doesn't really matter.
Assuming the spring is under load at all times and cannot touch or be touched by the rotating assembly.
Its all about having the spring force applied in the opposite direction of what is the expected rotation to accelerate.
rule is simple, trace a line/place a ruler from your spring anchor on the static position (intake) to the rotating anchor location when at WOT.
if this imaginary line crosses the rotation center min and max rotation, the spring force will apply an inverted force on the disc (the throttle axis),
and will mimic the same as you pressing the pedal to accelerate.
There are 4 combos possible depending on the linkage anchors, but rule is same, the line must not cross the center in between the 2 states.
Here's a quick and dirty drawing of one combo where both spring and accel cable anchors are on the lower side.

[Image: Screen_Shot_2018_10_03_at_14_34_49.jpg]

73 modified Grandé 351C. Almost done. 
71 429CJ. In progress
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#3
(10-03-2018, 07:55 AM)Fabrice Wrote: I'm not familiar with your setup and it actually doesn't really matter.
Assuming the spring is under load at all times and cannot touch or be touched by the rotating assembly.
Its all about having the spring force applied in the opposite direction of what is the expected rotation to accelerate.
rule is simple, trace a line/place a ruler  from your spring anchor on the static position (intake) to the rotating anchor location when at WOT.
if this imaginary line crosses the rotation center min and max rotation, the spring force will apply an inverted force on the disc (the throttle axis),
and will mimic the same as you pressing the pedal to accelerate.
There are 4 combos possible depending on the linkage anchors, but rule is same, the line must not cross the center in between the 2 states.
Here's a quick and dirty drawing of one combo where both spring and accel cable anchors are on the lower side.

[Image: Screen_Shot_2018_10_03_at_14_34_49.jpg]


That is a pretty neat diagram! 
I'm still kicking myself for loosing all the photos of when I pulled the car apart.
  Reply
#4
(10-03-2018, 10:59 AM)Bentworker Wrote: That is a pretty neat diagram! 
I'm still kicking myself for loosing all the photos of when I pulled the car apart.


Its not that neat, but it speaks way better english than I do Smile
Just remember that the "line" must never cross the center and you'll be safe.

73 modified Grandé 351C. Almost done. 
71 429CJ. In progress
  Reply
#5
it wasn't neat enough and confusing (the wrong colours and no line)
[Image: Screen_Shot_2018_10_03_at_14_34_49.png]

73 modified Grandé 351C. Almost done. 
71 429CJ. In progress
  Reply
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