So, being that I can't drive it now, my mind has been wandering to the dual Strombergs on my XJ6. Maybe it's because I started out with MGBs, but I am anything but a big fan of ZS carbs. It's probably just a psychological thing, but I find myself wishing I had a pair (or a trio!) of SUs under the bonnet.

So, unless I am mistaken, I have the following options:

1. Leave the Z-S in place and get over it. Perhaps remove the second Throttle butterfly.
2. Dual SUs, like the home-market cars, but avoid the AED.
3. Triple SUs as fitted to the E-Type.
4. Triple Weber/Dellorto sidedrafts.
5. Retrofit Later Fuel Injection System.
6. Develop and install Megasquirt powered fuel-injection system.

Have I missed anything?

I am aware that these range from "simple" to "quite difficult", BTW.

As for these various options, does it generally make sense to pursue other modifications if I take any of these routes? I'm thinking along the lines of a Series III head, for example.

Tom

 

I've owned one car that had carbs and it was converted. I had an 84 VW Rabbit convertible, with a Scirocco 16 valve swapped in and, being less experienced and patient at the time, could never get the cis mechanical fuel injection just right so I ripped it all out and put 2 40mm delorto sidedrafts on it. Loved em, absolutely loved them. The sound, the throttle response, it woke that engine up and they were easy to tune and never had problems starting the car. Wrecked it back in 2006, still kick myself for that one. I would love to put triple webers or delortos on an XJ6. Wouldn't be the best for fuel economy but it's not like it ever will be, anyways. I might be able to get 18-20 mpg for a stretch if I hypermile it on the highway but that's about as good as it'll get on the stock efi and trans in a s3.

Remember that since it's carbed now you'll have the added job upgrading all the fuel lines, the pump and probably the tank changeover system. Megasquirt would certainly be interesting but I would think not worth it unless you're willing to develop a crank sensor to run a wastespark coil. If you're going to stick with a distributor it would likely be much cheaper and easier to just grab everything off a donor s3 and call it a day. I vote triple sidedrafts, more kick, more smiles and just seems more appropriate on an s1.

 

OK, mostly crickets here, but I'll update anyway:

I really have no current desire to fit fuel injection (Jaguar or Megasquirt) at this time, though I certainly do think it's a cool idea. Call me crazy, but I prefer the "flavor" of the carburetors at this time. Besides, it would be a big project either way, and I'm not ready for that.

Webers are also out, just because it seems like the wrong solution for this car. I also tend to prefer SUs over webers, if only because of familiarity.

That leaves me two options:

1. Dual SUs
2. Triple SUs

Dual SUs would have to come from a home-market XJ6, and thus will likely need to be shipped in from the UK, I'm guessing. I will need the following, I think:

1. Maniflold
2. Two carbs
3. Linkage between the carburettors.
4. Anything else?

Are there other models with dual SUs on a 4.2 engine? 420, perhaps?


Triple SUs would need to come from an E-type or a Mark X, I think? They would have to be the one-piece manifold type for a 4.2 to fit, I think, as opposed to the 3.8's manifold, which is 3 separate pieces. Also, while the Mark X manifold cannot be fitted to an E-type due to clearance issues with the bonnet, does the same problem exist with an XJ6?


In the end, I think I would prefer to have the car set up as it would have left the factory if it were a home-market car, but there's certainly some allure to having three SU dashpots staring back at you from under the bonnet!


Can anyone provide more details?


Tom

 

Hi Tom...

I've never done the conversion, so anything I could comment on would be hearsay...

Just did a quick search on another forum, just because I remember reading quite a bit on the topic..
Here is one great tread to get you started:
JagFORUM Logon

(UPDATE... Link doesn't seem to be working^, I'll try to email some other details)

I seem to recall selling some bits off a 420 to go on a XJ6, and the bonnet clearance was an issue.. There was a work around, but I can't recall what it was...

Cheers
David
Everyday XJ

 

Thanks, David. I will try and dig up the thread you were linking to. The Jag-Lovers site is not readily searchable through Google, and I forget to look there directly.

I do think that I will be trying to collect the pieces for an XJ6 dual upgrade, but now I have another question which may be answered in the thread you linked. The Jaguar carburetors do not seem to have a choke, instead relying on the AED. I have also seen people suggest that one remove the AED, so that leaves me wondering what do you use for a choke?

UPDATE: The thread David linked to does mention ways to retrofit a manual choke.

 

David: the link seems to be working just fine. However, I think you have to log-on to jag-lovers to see their stuff.

Boy, I like the people there, but their software is crap!

 

One of the posters in the thread to which David linked mentioned a photo album. That album is here:

Welcome to Jag-lovers - Members Photo Viewing Page

You will likely have to log-in to access it.

Tom

 

Believe it or not the AED to go with the SUs is still available, and you can also get parts to fix your own.

Magento Commerce

The main problem with these units is the switching on and off. Even in the 60s, people installed switches on the dash to switch them on or off, not relying on the rather primitive temperature devices that were used. The unit itself is perfectly good for starting the Jaguar engine, albeit it uses a lot of fuel to do so, hence people wanting the on/off switch !

 

I'm actually converting my car BACK to ZS carbs. Previous owner installed Weber down drafts that have totally jacked up throttle linkage, and the fuel air has to take (3) 90 degree turns before it gets to the engine.

I think this is a cool way to do injection, as it looks totally stock:
TBI Components

 

By the way- triple carbs would be overkill without XKE compression and cam profiles. They do look the part though.

 

I hear you on the compression and cam, Sable. If I end up going for triples, it will only be because I find it first/cheaper. I do have a line on a pair of SUs, so I think I may take that route.

Not cheap, though, once you factor in getting the carbs rebuilt and finding the inevitably missing pieces.

Here's an idea: Why not mount the Z-S on the SU manifold? Eliminate the oddball secondary throttle plate arrangement, etc.

Tom

 

Another interesting idea, but I really wonder about the wisdom of not having a crossover tube between the carbs to reduce any vacuum pulsation.

RUSTY HEAPS » XJ6 Secondary Throttle Removal

Also, I was able to confirm that Mark-X/420G bits will fit on an XJ6, though there may be clearance issues with the intake plenum and/or the front carburetor.

Tom

 

Good idea to get rid of old strombergs. Just looked in the garage, and found a triple carb manifold from a 3.8 Mk10 and 1 2"SU. The manifold has a slight upward tilt on it, but I think the flanges would have enough meat in them to enable machining to alter the angle. As it is, the top of the SU sits 4'' above the top of the manifold/engine flange. Outside face of SU is 10" from flange.
There is definitely no difference in cams on 3.4 Mk2 through to S2 XJ6 4.2; the E type had the same cams. It went well because it wieghed half a ton less than saloons. Compression on any of those motors was normally 8:1, with 9:1 on special order. Easiest conversion would be the complete setup from a S1 XJ6, or 420. I assume one of our brethren in the UK would ship it over for you.

 

search downdraft conversion.

https://www.jaguarforums.com/forum/x...60/#post581052

 

Geneo: thanks for the suggestion, but I'm not a fan of the Pinto carbs...

 

yes webers are used on Pintos; in formula cars, if you know what they are.

 

Don't worry, Geneo, I'm just playing. However, Webers don't interest me at all, especially the downdrafts.

I have found that those who do prefer the Webers are generally more familiar with them than the SUs, and vice-versa. Indeed, because I am mostly familiar with SUs, I tend to prefer them; hence my disinterest.

 

So what path did you decide upon? I'm thinking of the same thing and would love to know what you did. The triple DCOE option looks interesting too.

 

I bought a rusted hulk of a 1971 German export XJ6.
Paid $1,000.00, in California, 1994.
I gleaned the Nardi steering wheel, dual HD8-SU carbs/AED, 4-speed electric OD manual stick, grille, interior, pedal boxes, master brake & clutch cylinder. The nicest piece, that I got as a bonus, was the Becker Mexico stereo. I'm going to hard wire an iPod cable to create a rolling jukebox, plus I have iHeart Radio.
Sold several hundred dollars of trim parts but still have the above, mentioned.
I bought the manual choke conversion kit for the SU's and the carbs run perfectly. The throttle shafts were line-bored. I fixed the stock Jaguar (typical BL/BS factory crap) throttle shaft bearing, at the firewall. Put in a real bearing and now works smoothly.
1975 is the saboteurs' party year at the factories.

 

Well, I have still done nothing on this front, though I have a dual SU manifold, two sets of HS8 carbs (one from a Rover so I can steal the manual chokes), plus a triple HD8 setup from a Mark X.

My current thought is to rebuild the Jaguar HS8s with Rover manual chokes and see how that turns out. I sure do wish that I had that manual overdrive transmission, though!