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Zedyone_kenobi

Master Triple Carburetor Linkage set up instructions

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In tinkering with my linkage for a few days (read as weeks) I thought I would try to compile a list of things to do while setting up a triple carburetors linkage. This list is not at all perfect, and could and should be edited, but should be enough to get your carbs running well and sync’ed up. This will NOT go into jetting, as there are a bazillion threads on that. This has everything to do with getting the mechanical linkage as reliable as possible.

These instructions assume you have a proper working Engine and carbs. Leaky carbs and vacuum leaks can throw you into a world of pain and frustration we that dare not venture into.

So let us start some simple tools:

Flat head screwdriver, small and large

8, 10, 12, mm wrenches (the more the better)

Needle nose pliers (because, well, I have stubby fingers)

Flash light

SK synchrometer (you have to have this to balance the air flow through each choke. Do not be cheap, spend the money on this)

Starting configuration:

Okay you have installed your triples on your manifold, GREAT. The fuel line is hooked up and you are getting about 2.5-4 psi into your webers. I have never found THE RIGHT setting for fuel pressure. I run 3 psi, so keep it around these values and you should be okay. For this discussion I use certain terms.

Lets Review, When I say:

Actuation Rod: This means the long rod that is held by rod ends that are screwed into your manifold

Actuation Arms: These are the Arms that attach to the Actuation Rod and work the carbs Throttle Arm

Throttle Arm: The arm that is physically part of the weber carb that opens the throttle plates.

Ball Rods: These are the adjustable length rods that attach the Actuation Rod to the Throttle Arm. Some kits have ball and socket ends, other have little rod ends. These are interchangeable.

Throttle Cable Arm: This is the arm that is attached to the Actuation Rod that the return spring and Throttle cable attach to. (your configuration may vary as to where you have your return spring)

Starting Configuration:

Adjustable Ball Rods are off the car and have their length set somewhere in the middle of the min and max length. This gives you adjustability either way should you need it. You can record the length of the rods in your journal, but as long as they are the same then you should be good.

Actuation Arms for each carb are on the Actuation Rod, but NOT tightened

Throttle Cable Arm is on the Actuation Arm, but NOT tightened

Air balance screws are all the way in.

Use flathead screwdriver to remove the progression hole cover. Shine a light into the hole. As you turn the idle speed screw clockwise you should start to uncover the first progression hole. Turn the idle speed screw counterclockwise so that upon any application of the throttle the first progression hole will be uncovered. This is a close enough setting to get you started. Your idle may be way too high or too low, but this should get the car running. Replace all the covers to the progression holes

Attach the ball rods to the Actuation Arms and Throttle Arms for each carb

Attach the return spring to the Throttle Cable Arm

Adjust the Throttle Cable Arm so that it has some tension on it. Tighten the screw or nut on the Throttle Cable Arm. This applies a closing force to push the throttle plates closed. You have to have this, as the internal return spring in the webers is not strong enough to do the job alone. NOTE: adjust the Throttle Cable Arm so that at 50% throttle the throttle Cable is perpendicular to the Throttle Cable Arm.

Start the car and let warm up completely. This is why we had to attach the Ball Rods. Makes starting MUCH easier. After the car is warmed up. Loosen the Actuation Arms again. The Throttle Cable Arm will snap back with the force of the return spring. This is fine, we will put that preload on back on it before we are done. We just want to get the carbs right first, then hook up the linkage.

Record the values of air flow through each choke (6 of them) with the SK meter:

Carb#1 ________, _________

Carb#2 ________, _________

Carb#3 ________, _________

We have two methods to effect this value. 1) The idle speed screw can raise or lower this number, and 2) we have the air balance screws that can only raise this value.

For ease of explanation, we can use an example:

Carb#1 ____5____, ___4.5______

Carb#2 ____4____, ____5_____

Carb#3 ____3____, ____4.5_____

First thing we want to do is balance each carb individually. Use the air balance screws to bring up the value of the low reading for each carb to match the high reading, so your new readings should be this:

Carb#1 ____5____, ___5______

Carb#2 ____5____, ____5_____

Carb#3 ____4.5____, ____4.5_____

Now that each carb is flowing the same individually, we have to sync them to each other. Before we mess with the idle speed screw, you must loosen the Actuation Rods first! After that is done, use the idle speed screws to set all the values to the lowest value, in this example, 4.5, so the end result should look like:

Carb#1 ____4.5____, ___4.5______

Carb#2 ____4.5____, ____4.5_____

Carb#3 ____4.5____, ____4.5_____

Congratulations your carbs are flowing the exact same amount of air to each cylinder! HUZZAH!

Now you can adjust your idle speed as necessary. To do so, Turn each idle speed screw the SAME exact amount until your desired idle speed is reached (950-1050 rpm is a good place to be)

Tighten your Actuation Rods

Preload the Throttle Cable Arm with a spring force and then tighten the Throttle Cable Arm.

You can now start to worry about mixture, jets, tip in, transition etc. your linkage should be spot on.

This is my practical approach to setting up a linkage for the first time. I tend to never adjust the Ball Rods to do any fine tuning. I like to keep those things exactly the same. That is not to say you could not use them. But I find it wise to keep as many things mechanically set on each carb instead of relying on linkages to get it right. The carb has less chance of loosing a setting in my mind.

Please add any advice or comments on this as you guys see fit.

Edited by Zedyone_kenobi

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Great topic again Stephen!

I have thought about this and have been only able to resolve as:

There are two targets:

1. Idle Balance

2. Off-Idle Balance

Method#1

  1. For setting idle, just the stops on each carb should be used along with the air bypass screws to ensure even flow for all carbs using an SK Syncrometer.
  2. For setting Off-Idle there is no adjustment. Just ensure the ball rods are exactly the same length as measured off the car. Fit them at idle and take up all the slack by pulling upon the Actuation Arms as you tighten them to the Actuation rod.

Method#2

  1. For setting Off-Idle, balance at 3k rpms by moving only the Actuation Arms and locking them to the Actuation rod.
  2. Set the idle with air correction adjustments and stop adjustments .

The bottom line is that the linkage adjustments either compromise idle or they compromise off-idle.

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You are of course correct !

Personally I also belive that you should leave the Ball rods the exact same length if you can. Very small adjustements are probably okay, but many turns difference is not what I would want.

If I had to choose, I choose idle...

I believe having a rock solid idle is more important than being a few degrees off in flapper angle when you are 50% open.

But like anything mechanical there is a compromise. Now if we can just make those nifty ball rods were were talking about in the garage! :)

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This is a good thread, i hope someone makes thread about DIY linkage... cause i need to do one. *looks at empty wallet*

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I agree, I read this thread a few times prior to setting up my linkage.

Koalia, not sure if you LITERALLY mean DIY linkage (like making your own actuation arms, throttle levers, etc). But a lot of individual parts are available via piercemanifolds.com. And not to plug my own post, but for some ideas...I cobbled together my own throttle cable conversion for my triple install. Hopefully it can give you a few good ideas.

http://www.classiczcars.com/forums/articles-our-members/50008-weber-dcoe-throttle-cable-install-%7C-parts-list-basic-descriptions.html

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This is a good thread, i hope someone makes thread about DIY linkage... cause i need to do one. *looks at empty wallet*

Here is an economical DIY way.

Parts:

- 3 rod ends (match thread to the holes on your manifold) make sure you have the right eye hole diameter for the rod

- 1 rod

- 4 door hinges (to replicate cannon lever arms)

- bicycle cable assembly

- hardware

Work:

- install 3 rod ends

- install rod

- separate door hinges, bend door hinge (one side with two pin holes) and drill holes for rod ends, install on rods and fasten with hardware

- fabricate a push rod with rotating ends and connect to the carb arm and the lever arm

OR

4 bicycle cables:

1 to each carb with the other ends tied to the same small rectangular bar.

The forth bicycle cable connects the center of the bar to the accelerator cable.

You will need to design and develop the end hardware and stand offs to make it work. (you may be able to use small wheels as pulleys too.

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does anyone make the actual rod that just goes in or the only way is the cut and weld the original?  I would like to keep it with just a rod and not put a cable for now.

Edited by hatepotholez

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37 minutes ago, siteunseen said:

Do these Zs jump around for anybody else or are my eyes bad?

zwave.jpg zwave.jpg zwave.jpg zwave.jpg zwave.jpg 

Hate to be the bearer of bad news, Cliff.  Time for a trip to the eye doc.  👀

Dennis

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3 hours ago, siteunseen said:

Do these Zs jump around for anybody else or are my eyes bad?

zwave.jpg zwave.jpg zwave.jpg zwave.jpg zwave.jpg 

 I'd wait to see the Doc. They're probably just flashbacks.

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Here is an application of the 280z linkage.

The shepherd's hook fits in a slot in the receiver. It can expand and contract.  You can cut it to length and the end is hidden in the receiver.

Sometimes you need to screw the heim joints up so that the throttle rod across the manifold is aligned with the shepherd's hook (in the photo below it looks too low)

Sometimes you also have to relocate where the bracket bolts to the firewall for left/right alignment.

The angle of the arm on the receiver looks nice below. You can loosen all 3 lever push arms so that the main throttle rod across the manifold can be rotated to achieve this.

 

Attention to details helps!

 

 

 

 

image.png

Edited by 240260280
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