Thats an interesting approach. I will look into that as well!

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1969 w108 280s

So I am digging this back up...

I have been extreamly irritated with my Zeniths. I cant seem to go more than a day or 2 without carb issues, even after replaining and partial rebuilding.

I am looking into microswitch options and here is what I am finding...
A NOS Microswitch may be a good answer. Attached is a general diagram of what I think may need to happen but I cant seem to put the pieces together.

http://www.jegs.com/InstallationInstructions/700/741/741-15640.pdf

From what I can tell, the 2 wires from the current MB neutral idle switch would go to this microswitch. The thing that im am missing is the actuating arm,
Does that need to bump into something or is it just a stand alone thing that does what it needs to all by itself?
I might be over thinking this but am I?

***Edit***

Now that I think/re-read about it more. The actuating arm needs to hit the throttle linkage at some point to activate the thing, (just like Scooter said before)..but which way? When throttle is off (no gas pedal) the actuator arm needs to be pressed or?

Found this too...

http://www.streetlegaltv.com/tech-stories/power-adders/nos-powershot-125-nitrous-plate-system-installation/

So I need the microswitch to be activated when the linkage returns to idle position...


Sorry I am thinking out loud but I might finally be getting it

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1969 w108 280s

So the Webers and the switch...

I will be starting this conversion tonight so I will keep you (ya'll) posted
It may take a few days though.

Ill be back with pics and a write up

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1969 w108 280s

Good luck! Curious how it will turn out. Have you settled on the NOS microswitch?

The secret to set Webers up properly is to adjust the idle stop screw so the transition holes above the throttle are not exposed at all. Once the engine has warmed, use only the idle mixture screw to set the idle. This is critical as on Webers it's not an air bleed screw as on the Zenith. Rather, it feeds a pre-mixed mixture. If you use the transition holes to set your idle, check for vacuum leaks.

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1968 Mercedes 280S - The Demon Car

Hi mosu
I went with a 2 pin JEGS microswitch, samething as a NOS switch but not really branded.

Good to know about the idle mix screw, thanks. I have found abunch of info on tuning the Webers so I think this may go pretty good

I did find this... OZBENZ - Australian & New Zealand Mercedes-Benz Forums • View topic - Dave's Weber Carby Conversion 'How To' Thread - W111/108/114 so I will base most of my steps from here but not removing the manifold.

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1969 w108 280s

So far some observations and a question....


Even it being a JAM kit there are a couple of odd things.
1) The fuel inlets need to be swapped on both carbs. That way the fuel line is not directly over the manifold
2) The linkages supplied for the carb to throttle linkage is indeed too short. When the carb is extended to full throttle the supplied linkage, it gets bound up and throttle sticks to full WOT. I needed to extend the linkags as listed in the OZBENZ thread to prevent this.
3) BOTH brackets for the throttle linkages do need to be ground down abit as they do hit the manifold...



Now for the question
I have an air return line that goes into the manifold and comes from an air pump down by the powersteering pump. Aparently it is part of the blow by system from the crankcase where air is recycled back into the engine to reduse emissions. This pipe is in the way for the new linkage set up.

I assume it is ok to block that off at both ends as it is just a return line for dirty air or no? ....If not Im screwed

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1969 w108 280s

Moving along...

I have deleted the emissions air return. I was not able to locate a correct plug for the port so I just hacked off the tube and piched it with a hammer to make it air tight. Not the best way but it will work for now. The other end has been done in the same manner.

Becuase of the manifold and the way the carb is manufactured I needed to hack almost 5mm off of one of the mounting bolts for the front carb, (driver side front bolt). The bolt was just too long to go up through or down through. An easy fix and still had plenty of thread to secure it down.

Both carbs have been mounted and are ready to be plumbed. I still need to adjust the linkages between the throttle and pivit arms before it gets fired up.

After that is the microswitch...
I have only been working on this about an hour to two hours a night, so progress is slow. I am hoping to be back on the road by Friday.









***Heres the write up...http://www.peachparts.com/shopforum/vintage-mercedes/363544-w108-zenith-weber-conversion-w-auto-trans.html ***

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1969 w108 280s