a relevant question on zenith carburetors when fiting them in the engine

deQuincey

deQuincey

Quousque tandem...?
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take a look to thus picture,



ECA4F871-0EEA-4A96-9152-460C59E45587.jpeg


before you install the carbs in the engine on top of the inlet manifolds your accelerator linkage has those bars E And D resting against the plate of the front support of the carb linkage,

specifically the top of bar E moves the front end of the carbs linkage to sit against that plate

in the mentioned plate there is a bolt that is used to rise the rpms to 1700 while making carbs synchro, and that must not touch the carb linkage during normal operation
 
before installing the carbs, the front end of the carb linkage (circled in green in the next pic) sits against the plate,

but if i install the carbs now, the two spacers (the one with the knurled nut at the rear and the other at the front) moved the front end of the carb linkage 4mm away from its resting position

2E23CCFA-F845-47E7-8582-6CD5A4A1A855.jpeg


see here the front carb linkage end in the sitting position in green

and the spacer of the front carb in red
 
i meassured those two spacers and their actual length is 46mm

i have found no information as settings of those two spacers, so my guess is that there is not a fixed value

so here is my rational:

if the basic requirement is that the carb linkage has to sit against the mentioned plate, i must change the length of both spacers accordingly, so when the carbs are at rest position the mentioned carb linkage contacts the plate

thus i have to increase the length of the spacers to 50mm

i have done that, and now with the spacers in place the front carb linkage sits on the plate correctly


question: do you agree ?

calling e9 zenith carbed owners, i.e. @Stevehose @sfdon...
 
The picture you show of the two bell cranks next to one another appears to indicate that the new one is larger than the old one. Specifically, the distance from the center hole to the "ball joint" attachment point for both linkage rods appear to be farther away from the center hole. Can you confirm this, or alternatively, is my thought merely due to the fact that the newer bell crank appears larger because it is closer to the lens of the camera?

If my thought is correct, the arc of the bell crank will be different, and the 252 mm and 326 mm settings for the linkage rods will not put the upper attachment point on the shorter linkage rod in the right place. Both of these rods needs to be shorter to accommodate the longer arc.

More importantly, your old bell crank does not look to be defective. And I would think that if there were a problem in that area, it would most likely be with the two piece bushing that goes inside the bell crank where it installs to the engine, or perhaps a missing end clip (which had been missing on my car). The more likely trouble spot is that rubber attachment point at the top of the accelerator pedal, which over time becomes hard, develops cracks, and deflects either upwards or downwards when you step on the gas.

What problems were you having that started you down this path?
 
dear @Ohmess
i will answer in your text

Ohmess, post: 303442, member: 1367"]
The picture you show of the two bell cranks next to one another appears to indicate that the new one is larger than the old one. Specifically, the distance from the center hole to the "ball joint" attachment point for both linkage rods appear to be farther away from the center hole. Can you confirm this, or alternatively, is my thought merely due to the fact that the newer bell crank appears larger because it is closer to the lens of the camera? IT IS THE LENS OF THE CAMERA, THEY ARE ALMOST EXACTLY THE SAME SIZE

If my thought is correct, the arc of the bell crank will be different, and the 252 mm and 326 mm settings for the linkage rods will not put the upper attachment point on the shorter linkage rod in the right place. Both of these rods needs to be shorter to accommodate the longer arc.

More importantly, your old bell crank does not look to be defective. And I would think that if there were a problem in that area, it would most likely be with the two piece bushing that goes inside the bell crank where it installs to the engine, or perhaps a missing end clip (which had been missing on my car). The more likely trouble spot is that rubber attachment point at the top of the accelerator pedal, which over time becomes hard, develops cracks, and deflects either upwards or downwards when you step on the gas.

What problems were you having that started you down this path?

OK, SO THE BELL CRANK, THE OLD IS DEFECTIVE, TRUST ME, THE TWO SMALL END BALLS OF THE BELL CRANK MOVE IN ITS PLACE, THEY DO NOT STAY STEADY IN THEIR PLACE

THANK YOU FOR THE DIGRESION
 
So, are what you are asking is why you have to lengthen the 2 linkage connectors longer to fit to the cross rod linkage arms? I see that your chokes are closed which will put the carb linkage in a fast idle state which may be causing the linkage to be open more, have a look at that, it might be holding up somewhere. I have never seen an actual measurement for these linkage bits, they are never the same car to car as they adjust to each individual setup to balance the linage pull on the carbs

Thanks, Rick
 
deQ can you confirm that the new bell crank is different?

How did you realize they rotated, what happened when you pushed down on the accelerator? If it happened to you, it has or will happen to some of us so knowing the symptoms is important.

What about using a punch on the old one or a single tack weld to stop the ball linkages from motion?
 
stphers said:
So, are what you are asking is why you have to lengthen the 2 linkage connectors longer to fit to the cross rod linkage arms? I see that your chokes are closed which will put the carb linkage in a fast idle state which may be causing the linkage to be open more, have a look at that, it might be holding up somewhere. I have never seen an actual measurement for these linkage bits, they are never the same car to car as they adjust to each individual setup to balance the linage pull on the carbs

Thanks, Rick
Click to expand...


thank you, Rick, you were right
the question is precisely that, fast iddle cold vs operation temp,

se here.

20201108_004549.jpg
20201108_004641.jpg
20201108_004723.jpg
20201108_004814.jpg


with regard to the position of the lever, low vs top notch, the final point of the carbs sits around 4mm higher,

so nothing was changed except that I did not considered operating temp vs cold start

that k you
 
bavbob said:
deQ can you confirm that the new bell crank is different?

How did you realize they rotated, what happened when you pushed down on the accelerator? If it happened to you, it has or will happen to some of us so knowing the symptoms is important.

What about using a punch on the old one or a single tack weld to stop the ball linkages from motion?
Click to expand...

no different they are identical

did not realized in operation, only when disassembled

there was not enough meat to use a punch

regards
 
Porsche and Alfa vendors sell new balls with a threaded end, I have taken a grinder to the backside of the original balls and then punched the old ones out and fitted those or if they are just loose but still OK , a little spot weld or braze will hold them tight.
 
so went to the car and did it,
i went back to the previous meassure,


it is very curious, i never checked this, but now i am aware of the difference

normal operating temperature, buterfly is wide open, the lever sits lower when compared to fast iddle, see white marks)

367A2DEB-1BB1-4E48-BABE-146C0E838BCD.jpeg


1D124685-DC46-43F5-9386-543886CCABE0.jpeg




IN THIS CONDITION, THE 2 LINKAGE CONECTORS ARE 46,3 AND 46,6 MM RESPECTIVELY WHEN THE LINKAGE TOUCHES THE REST PLATE


when we change to fast iddle the lever sits higher and distance is 4 mm more, till 50mm, and the linkage does not touch the rest plate, but this is not the normal working condition

4592FE3E-525C-423B-821A-30F04F4DA2C4.jpeg


91C14EA7-BFEF-45C0-BE9E-82D752BB2E63.jpeg
 
Last edited:
bill said:
DeQ: convert to D-Jet, no more carb problems! (...as long as it works....)
Click to expand...

oh Bill, thank you, but
i dont have carb problems
did i gave the impresion that i needed to change carbs ?

i am only sharing my experience on zeniths

as a side note, and IMHO:
i have no intention to convert to any other system
zenith carbs are the most interesting fuel feeding system for the e9 coupe (for a 3.0 CS)
you could consider zeniths as the summit of carb technology meanwhile fuel injection was only starting

zeniths were able to develop automatic choke, nice iddle, good transitions and powerful torque at high revs, they are reliable and solid, superior to most of other carbs of their era

true is that not everyone is able to deal with them these days, DIY is the best recipe, and knowledge is important, that is why i am sharing this
 
deQuincey said:
oh Bill, thank you, but
i dont have carb problems
did i gave the impresion that i needed to change carbs ?

i am only sharing my experience on zeniths

as a side note, and IMHO:
i have no intention to convert to any other system
zenith carbs are the most interesting fuel feeding system for the e9 coupe (for a 3.0 CS)
you could consider zeniths as the summit of carb technology meanwhile fuel injection was only starting

zeniths were able to develop automatic choke, nice iddle, good transitions and powerful torque at high revs, they are reliable and solid, superior to most of other carbs of their era

true is that not everyone is able to deal with them these days, DIY is the best recipe, and knowledge is important, that is why i am sharing this
[/QUOTE
You never have problems, DeQ, only solutions!
Right now my D-jet isn't working so I am envious of the days I had Zeniths or Webers with their non-electronic simplicity. I'll figure it out sooner or later...
Click to expand...
 
My coupe is a '74, that originally came with Zeniths. The Zeniths had an air adjustment in addition to a fuel mixture adjustment (other carbs including Webers have only an air/fuel adjustment.) Apparently the '74 Zeniths were the most difficult to tune due to the separate air/fuel screws. Have you had experience with them?
 
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