Greetings. I was reading the Jag Shop Manual on the proper procedures on adjusting carbs, and I must say that it is written poorly, and lacks any useful pictures. The description is confusing and references parts which are not revealed in the manual.....very poor indeed. I also have a Haynes manual which is better with regards to pictures and diagrams, but still lacking. I thought that someone would have posted a detailed write-up at this site, but I have been unable to find anything. Is there already a detailed write up on this site?

 

Well, I went ahead and dove into the carb adjustment, even though the manuals are so vague about the procedure.

I loosened the set screw that combines the shafts of the two carbs, then backed out the Idle Set screws about 3 turns....manual said to the point where the screw is no longer making contact. Well, that seemed impossible, maybe due to the choke attachment....not sure. I then tightened the rod set screw after getting them to where both carbs were beginning to move at the same time as I moved the throttle linkage.

I then dialed the Idle set scres back in 1.5 turns, and started the engine. Then, backed both set screws out enough to get the idle down to around 700. I then tried a vacuum meter to balance them, but that did not work, so I resorted to the rubber tube to the ear trick. This actually worked great....really amplifies the hissing sound when placed right in front of the carb. This let me know that the outter carb was running too rich, and that mixture screw which they say "Never adjust" had been loose, and clearly was not right. As a rough measurement, I used a micrometer to measure the inner carb Mixture screw length and compared it to the outter carb....huge difference. The inner was about 17.5mm, while the outter was only about 12 mm. So I dialed out the outter carb to about 17mm and cranked up the engine. This made a huge difference, and then I tweeked the two Idle screws until I had the same hissing sound. Now she idles great at 700, and has a quick responsive rev:

Inner Carb "Do Not Disturb Mixture Screw" at about 17.5mm:


Outter Carb being increased from 12mm to 17mm:

 

Vacuum Line Question:

Before rebuilding these carbs, the vacuum line coming off the outter (front) carb was broken at its bend, and then not connected on the other end. Now I just have a plug on it, but can someone tell me where the vacuum line is supposed to run to? Pics:



The rear carb's vacuum line goes to another vacuum device.

 

What is the exact model of these carbs? I have a '76 XJ6C and am looking for a pair of these.Or is there an upgrade?! Does anyone have experience with the aftermarket fuel injection kit?

 

It connects to the vacuum advance on the distributor.

 

There is one on SU’s, but probably not much help to you.

https://www.jaguarforums.com/forum/a...17/#post928571

 

To adjust the mixture on Z-S carburetors you need a jet adjustment tool. Unfortunately, some Z-S carbs are adjustable and some are not depending on the application. I found that out the hard way.

Z-S mixture adjustment tool