XJ throttle cable conversion, XJ motor into 420G

Greetings Gents.

hard to know where to ask these questions, XJ, or Saloons

My issue is to install a better throttle conversion than I presently have in my S2 XJ motor into 420G

My new intention is to use the XJ cable, however the throttle connections in a 420G, and other older Jags, is by rods & levers, so this is not perfectly straightforward

see pic

The XJ has a cable pinned to the accelerator pedal rod, as pictured

There are several ways I can go about this

  1. modify accelerator rod (Part 7 in 420G pic) to accept XJ cable end

  2. Install all needed internal accelerator parts (pic 2) from a wrecked XJ

  3. I yesterday obtained a modified accelerator pedal & linkage cable setup from a wrecked MKX that had a V8 conversion. It does not fit into my vehicle without some further mods

My present system connects the 420G and XJ parts together, been driving it 12months, but has a flaw

Hi Tony, what are you using at the moment?
How about an eccentric disc or lever like on more modern throttle bodies and an L-shaped bracket that holds the cable sheath, at least that is what I imagine not having seen the SII setup. essentially part 8 or 13 pulling on the cable? If you start with a lever you can adjust throw, but of course you would need a moving pinion (like part 11 or 17 I guess) so the cable won’t be bent. Or you attach the cable at 11 and put a bracket on what would probably be the firewall. Would that work? Attaching the cable is easy, drill two holes and put threads into one, or clamp it with a screw head, maybe.

David

thanks for the incredibly quick reply…I was still editing in the excerpts into the post, and I will add some pics later on

No problem. Is it fuel injected? Then I know what it looks like.
The pictures make me less secure about what to think but generally you might want to keep everything original and restrict all modifications to the business end, where the cable attaches. An L-bracket and a pinion with mount, would that fit?
And: How did you attach the cable to 7?

David

not FI. late Carbie S2, has twin HS8.

Parts Manual indicate little difference in FI vs Carb setup

If I go Route 1 (utilise 420G part 7)…there are a couple of ways

A) make a slot in far right end of rod, identical to XJ setup, attach in same manner
B) make an attachment to part 7 or 8, that pulls the cable down

in each case, I will need to fab an internal bracket/s to hold cable end, and drill a hole.

The big issue is cable travel and and throttle lever travel must be the same to get idle to WOT

Hi Tony - if you can get hold of a Series 1 throttle lever assembly (pg 22 72 in the parts manual) I can tell you exactly how to do it with little modification and only some light fabrication. The only problem might be that I’m assuming your car is RHD being in Australia. If you have access to that version of the throttle lever assembly and can attach a cable to it that pulls from the left somehow the rest is easy. Here’s a pic. You might notice also that the secondary shaft that the gold colored crank is on is a S2 XJ part. You don’t strictly need that cause it’s a standard 5/16" shaft and can be easily fabricated.

~Mike

Oh wait - I see that you are using a dual carb set-up. That image was of my triple SU 420G/Mk10 manifold and carbs into Series 1 XJ6. Nevermind

Thx Mike…is it possible for you to post that pic with arrows to the mods that connect?

I see that is a 420G manifold, with HD8s

its a long story, my conversion.
The replacement motor is an older $$ (not mine) rebuild with manual choke HS8

I could have swapped this manifold for the 420G tri-carb setup, however, I like the manual choke so more than the ASC, that I intend to keep it,

SO, your picture will be VERY useful, when l eventually refit the 420G manifold, but with triple HS8, using a XJ12 twin choke cable, and XJ throttle cable

I have the the throttle bracket parts from a S1 2.8 at hand, and my mate has a bucket of brackets.
can temp fab any brackets needed

I’ll post more pics tomorrow but in the meantime I can explain pretty easily. Everything on the bottom is the normal S1 assembly. All I did was cut off the arm that was there and weld that longer silver arm with the three holes in it’s place. I made that arm the same size as the gold arm because there was no need for any sort of progressive opening.

The gold arm is an off-the-shelf part that Redline makes for Webers - 5/16" shaft size. Connecting them together are a male and female heim joint threaded into each other.

The small, upper shaft is a S2 XJ6 throttle shaft - just like part no c45483 in your 3rd pic. It connects to the main throttle shaft of the manifold just like a S2 would.

The small, upper shaft is carried by a stand I made and bolted to the S1 throttle assembly. The shaft is held in place by the gold arm and an off-the-shelf 5/16" collar that you see on the other side of the stand. There’s also a brass bushing in there that’s hard to see.

And that’s it. I spent a good amount of time trying to figure out the least complicated way to do this in terms of fabrication and buying as little as possible. It seems to work pretty well.

~Mike

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Tony,

I may not get your point, but if I understand you correctly, now you have a 420G car and a 420G triple carb setup and only an XJ6 SII engine between. Why doesn’t the original 420G rod and lever setup work in the first place, or, the other way round, why do intend to put a throttle wire in? You only state you’d like a better throttle conversion. What is wrong with the original setup?

Leaving that aside you might simply install a series Jag pedal with throttle cable


and the original SII bracket (as per your picture). The length of any SII cable should be sufficient. You’d have to fabricate a mounting plate though to install and operate the lever.

Good luck

Jochen

75 XJ6L 4.2 auto (UK spec)

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Hi Jochen…not quite

420G car, S2 XJ engine, 2 x HS8 with manual choke.

my original throttle conversion is not entirely satisfactory

I intend to run a XJ cable system to overcome the problem

your suggestion of transplanting “in cabin” parts of an entire XJ throttle is sound. I mentioned it earlier as an option, but getting all the parts may be a bit tricky, and some mods needed

to add further to the confusion, once I have my present setup working perfectly, I intend to re-install the 420G manifold, but NOT with tri HD8, but tri HS8, with manual choke control

will add some more pics later…I think I have arrived at a solution

I put a 3.4 XJ6 Engine in to my MK2 ,that has HS8 carbs with manual choke no real problems all lined up well to the MK2 linkage , a few modifications , only problem I had was , with 3 springs on the linkage , 2 on 2 Y brackets , and one on a long rod , the butterfly’s would not snap shut as crisp as I would like , so I added another Y bracket on the top , with a spring , as a quick easy fix , still running like it , as we all know access to under the carbs is very limited , may have a look over the winter to remove the top bracket to clean things up a little !

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Thanks Gents,

I see several methods are possible, I will add more pics later

At this time I favor a “universal throttle cable” with adjustable ferrules and nipples,
set up as per the XJ. The stock XJ cable outer may be a bit short for my application. It would be useful to know what length it is?

I note S1 and S2 have a different cable orientation

Thanks, your explanation makes sense of the pic…very neat job!
If you dont mind, I may request you to PM me some pics, as they would help me greatly in future with my triple HS8 “upgrade” …(a 420G MUST have tri-carbs…will post pics when finalised)

followed your posts with intense interest, great job.
As with the previous gent, I may pester you with a PM of “throttle pics”…rather than possibly bore the general XJ poster…it would be of interest to me to see what you did!

Thanks Tony - I may start another thread just for it later this weekend just for the sake of the archives.

~Mike

good idea…the new method of embedding pictures will greatly improve the quality of the archives imo

I should probably wait a week or two, for a few parts I ordered to turn up

attached are a couple more pics

  1. The S1 XJ bracket/cable, pulls outboard, instead of inboard like the S2

  1. pic of a S1 bracket, AND pulled the throttle conversion parts from a wreck MKX that once had a Ford V8 conversion…all brazed together from custom made parts

several ways to do things. Attaching the cable so that it has same travel as throttle is exacting

As long as you can adjust or measure the radius of the arm I wouldn’t worry much about that, the only question is where to attach, right?
I’d try to stay with the original pedal, but that’s me. Then a plate in the engine bay to which everything attaches. If there’s space.

David

thats correct, its harder than one would want though…I have practically ruled out an “in-cabin” XJ style cable, as it would foul the foot, without mods.

That leaves 2 obvious alternatives

Plan 1) attach the cable to item 8 (lever in 1st pic)…no permanent alteration to original parts

If for any reason, that does not work…2) Fit the accelerator pedal from the wrecked MKX to Ford conversion…some parts need removing and 2 holes drilled

Just awaiting for the parts to arrive, ordered universal cable/adjusters/stoppers for $35 from a motorcycle place to make custom cables

pics to follow when complete

thanks Gents for the inputs, now complete and road-tested.

I should have asked before I did it the 1st time :persevere: , as this new design overcomes the 2 problems with the previous system, and is easy to adjust, modify or replace.

No Jaguar Part was harmed, nor holes drilled

Part No8 lever, in the very first pic was used

Unfortunately I had modified a bracket previously or could have used the original Jag part, had to make a bracket, apologies temp made from scrap, return springs need finalise, and untidy wiring for my Engine swap, ongoing aircon project and other doodads

cable parts came from a motorcycle supply shop.
I should have made the cable a bit shorter, but can easily do that when the tri-carb setup is finalised

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