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Discussion Starter #1
I have Weber 45s on the 2L in my 1966 stepnose.

I had the carbs off and on putting them back on I and am struggling with a throttle linkage issue. The arm on one end of the linkage comes too close to the brake lines for my comfort. But if I adjust the linkage for more room, the throttle butterflies won't open fully. So my choice is to have the brake lines at some risk or to have a throttle that opens fully. I'm erring for safety now, but want full throttle!
I already removed the stop under the throttle pedal and have full movement there.
I could remove the bellcrank below the carbs and try to "adjust" one of the arms (cut and weld). Or maybe grind away part of the arm that comes too close to the brake lines. Or move the brake lines.
It does seem there is a lot of "slop" in the linkage, especially around the bellcrank. ie: if the pedal is too the floor, I can still push the throttle down a bit at the carbs and open them fully. Maybe if I fixed the slop the problem would vanish.
Anyone have any better ideas? Am I missing something?
Carl
 

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Discussion Starter #2
Just in case I wasn't clear..
Adjusting the linkage shorter or longer is no help. The problem is the "throw" is too long now. I need to achieve more throw with less pedal movement. The only obvious way I can think of is to remove the bellcrank and to slightly shorten the arm attached to the throttle linkage. Am I missing something?
C
 

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Where is the linkage hitting the brake lines? I'm guessing back at the firewall, where the arm that extends downward from the throttle pedal shaft is located at rest. I agree that you don't want your throttle arm resting against a brake line - if nothing else, the rattling will drive you nuts, but yea, eventually it will wear through.

Hard to say how to best fix it. If there is play in the four rod-ends that make up this linkage, then sure, replacing the rod ends should make the linkage more efficient. That would probably be a good idea even if you weren't having this problem - loose rod ends will eventually become so loose that they fall off. So, I would try replacing the ends first, and see if that solves it, before resorting to modifying the bellcrank.

I had this problem on my Duetto. What I did was to install a rubber bumper on the firewall that acts as a rest for the throttle arm - the bumper projects out further than the brake line, so the arm rests on it instead of on the brake line. This eliminated the rattle, protected the brake line, and made the bumper, rather than the carb butterfly, support the force of the spring on the throttle linkage. A quickee way of accomplishing this might be to slit a piece of fuel line, wrap around the brake line securing it with tiewraps, and seeing if it solves the problem.
 

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Discussion Starter #4
I pulled the bell crank out, and it looks to me that I can bend the short arm to make it a bit shorter. Actually, just a small change should have a big effect. But as this bell crank is sloppy anyway, I've ordered the centerline part. I'll measure that and compare it to the one I have first, before any bending. Since I'm digging around with this anyway, I'd be happy to install a now slop ball bearing bell crank...
Carl
 

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Getting a bell crank with no slop will probably solve most of the problem.
As you push the pedal down, the first bit of movement rotates the belcrank sideways instead of forward. Centerlines excelent part made mine work perfect !!
Randy
 

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I had this problem in my race cars decades ago. It came from the sloppy fit of the carb bellcrank as you surmised. I pulled this apart and made a bronze bush out of one I found of nearly the right ID.

Machine the outer diameter to a press fit in the bellcrank. Turn the bellcrank shaft on the other piece a bit (otherwise the insert gets too thin), then drill and broach the inner diameter of the bushing to a 0.002 clearance. Voila! Precision bell crank with no slop.

Thin steel shim stock works too, just doesn't last as long.

On my latest version, I just cut off the shaft and tube set and replace with a ball bearing. Even better.

There is plenty of throw. Be sure the throttle stop under the accel pedal is not too high - it will limit the WOT psoition. But don't drop it too much that you load the plastic push rod (from the firewall to the bellcrank).

There are enough adjustments that you should have no problem getting WOT and still closing on the idle stop. I never had less than an inch of extra pedal throw. BTW - back off the idle screws fully before adjusting the linkage.

With the throttle links disconnected, the lever arm gets close to the brake lines at the firewall under the rear carb. Adjust the stop on the mechanical throttle cable (stiff wire actually) to hold the lever in the closed position 2 to 3 mm away from the brake lines. You can even wrap the lines with a stiff, carefully bent steel shim stock. Watch this for signs of wear. Eventually I just welded a stop onto the firewall to keep the lever away from the brake lines.

Robert
 

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Discussion Starter #7
Robert, some good comments there... but I'll note a couple items. I removed the pedal stop completely a while back, still not enough clearance. And I want more than a2 mm of clearance at the brake lines. Your idea of a stop wended on the firewall is the best safety measure, I think.
Randy and all, I just received the Centerline bell crank, it is MUCH different than my original dimentionally. That is, it's short arm is significantly shorter, just as I was going to bend the original. It has some other subtle height differences. I will take photos and will report back on how it fits.
C
 

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Discussion Starter #8
So here's a picture showing the original bell crank compared to the Centerline one. You can see the short arm is significantly shorter on the Centerline version. Actually, it's probably possible to bend the original bell crank to be shorter too, although it might interfere with the carb support.
At any rate, putting the centerline crank on my car solved the problem. The throw is significantly shorter. I was able to even put the pedal stop back in the car and adjust it upwards towards the pedal. You can feel how much shorter throw the pedal is with your foot. And the movement is nice and smooth.

Here are some other bellcrank shots I found elsewhere on the forum.

So it appears whoever made the centerline crank knew that they where doing.
Carl
 

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