I have a 1977 XJ6C 4.2 series ll and want to know if anyone has done the conversion from Zenith 175CD-2 water choke thermostat carbs to the Weber carbs? I don’t understand how to do the replacement do I leave the water manifold behind the new carbs or remove it completely
Thanks Dave
Hi Dave - welcome to our forum!
What makes you want to put in Webers in the first place, if I may ask?
While Webers are wonderful pieces of machinery they are not native Jaguar and consequently need a lot of expertise and time or trial and error to be set up correctly.
An easy and straightforward way of getting things right is fitting a standard set of twin SU HS8 or HIF7 to the standard inlet and use the standard air filter. Sets can be had at a fraction of the price of new Webers and you may invest into a full overhaul with original parts and be set for the next 20 years.
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
2 Likes
You mean the twin downdrafts I presume?
Jochen, first thanks for the input. I was going to rebuild the original Zeniths but had a real problem finding the water choke thermostats. the ones on my carbs are shot and will not work. I didnt know about the twin SU HS8 carbs and don’t know where to find them but sounds like a good Idea. Are they set up to work with the water choke manifold that the zeniths use? I am not the best mechanic in the world but have got by for the past 70+ years but can use all the help and advise for sure Dave
Hi Wiggles Can you send me any pictures or give me instructions on how to install, I don’t know if I keep the water manifold that is behind the old carbs or remove then it could create a different problem all help and advise is greatly appreciated
yes that is what is in the kit with the adapters, having some trouble figuring out how to install the new carbs with the water manifold being removed and then not sure it will work with it removed. leaving it on I will have to modify the cross brace for the fender Thanks Dave
Hi David that’s awesome.
Maybe if you share some photos the group can help better everyone here v helpful.
I am new to Weber’s too, I promised myself that one day I would attempt to become very proficient w them.
In meanwhile here is a cool older ad someone posted several months ago I think it was another David
If your intent is to use 3 sidedraught carbs, they come with their own manifold.
Dave,
if you’ve got the Webers already, you’re in the game … usually a full set of Webers including intake manifold runs around 1/3 of the market value of an average car.
This would be an example of a complete set of SU HS8 carbs - just in case you haven’t bought the Webers yet https://www.ebay-kleinanzeigen.de/s-anzeige/vergaser-fuer-jaguar-xj6-serie-2/1628388208-223-1588. Apparently the aux carb is missing just as the original air filter box.
BTW, with twin HD8 carbs SI cars were measured at 186 DIN hp and that seems a sensible indication of power available with later HS8 carbs as well. With Stromberg carbs and US emission controls I doubt there are more than 160 on tap.
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
…and WAAAAAAY easier to setup!
If the Strombergs are identical to the E Type, did you tie up/remove the butterflies already? They say power is close.
If you want power, triple HD8 or the webers in the XKE…
Daves!
Would’nt a fuel injection system be much better?
I have a 78 xj 6 since new have never had any problems with
the injection system.
Walter
This comparison is interesting but I wonder how much better the car would go with a re-needle. I run UM needles in my '62 - standard. I know that it feels quite different if I run a richer needle. Might need different filtering, but maybe not far behind the Webers? Paul.
I’m not sure if it is relevant, but I do recall that the E Types fitted with Strombergs, although their claimed power output was down, were actually quicker to about 90mph than the triple SU equipped S1s. The smaller throats enhance low rev gas flow, which is arguably more important in a saloon car. It might be worth sticking with the original setup if possible; there must be plenty available. Webers will almost undoubtedly give you more grief than they are worth, not to mention vastly inferior fuel mileage.
1 Like
I’d suggest talking to @DavidBoger at everydayxj.com and seeing what easy solution he has on his shelf. He breaks many an old XJ and will surely have some working carbs.
Nick
Jochen,
I believe you are correct. IIRC, the US Series 2 E Types used a 3.54 diff, which, with the 5000rpm limit of a 4.2, would have restricted top speed to about 120mph. Even a Mk2 or XJ with 3.54 is a bit fussy. My S1 Sovereign has 3.31, and my E Types had 3.07, which were much more pleasant.
At the time, in the US how well a car sold was inversely proportional to its 1/4 mile time.
No: the 175 CD Z-S are a separate carburettor: the secondary butterfly arrangement was a manifold to which the ZSs attached, unique to the E Type, afaik.