Slightly Modified XJC Project

XJ
1

Hi All,

I’ve been lurking here for a while so I thought it was about time I posted something.

A couple of months ago I bought a 1975 XJ4.2C, I’ve owned a lot of (mainly British) older cars over the years but this is my first Jag. I’ve always fancied an XJC and as prices seem to be on the up I thought I’d better grab one before they are out of my reach.

My plan is to slightly modify the car to make it more reliable and driveable, I’m going to convert to a manual gearbox, fuel injection and electronic ignition, and I want to look at what can be done to firm up the suspension and sharpen the steering. A more rorty exhaust note couldn’t hurt either. More immediately I need to adjust the side windows and replace some of the seals, and I want to get rid of the terrible aftermarket sunroof. I’ll get the bodywork sorted as time and funds allow and i’m toying with the idea of reinstating the vinyl roof, not sure on that yet…

I settled on this car because it appears to be pretty solid, there’s no rot that I can see in the usual spots like floors, sills and boot. There are some bubbles in the area where the rear quarters meet the sills and at the base of the c pillars, and no doubt I will uncover some horrors as I dig into it!

The car has been unused for quite some time but went through an MOT without much fuss. The seller put on a new stainless exhaust for me and a nice set of Kent alloys.

The photos flatter the car as the paint is actually a bit of a mess. Good from afar but far from good as they say. I don’t know what colour it was originally, there is some evidence in the boot that it may have been light blue or possibly lavender, but I like the black on red scheme so I’ll probably be keeping it.

The interior is generally good with just a bit of broken stitching on the driver’s seat base, there are no rips and the leather looks like it will respond well to feeding. It’l need new carpets and headlining however.

At some point the engine has been replaced with a unit from a Series 3 Daimler that is reputed to have done only about 30,000 miles, running on carbs.

My first couple of months have been difficult with the car breaking down on only my second short trip. This was quickly traced to a broken wire in the engine bay. Quickly fixed but one of the jobs on my list is to replace all the engine bay wiring as there are 45 years’ of blue plastic crimp connectors to deal with.

The next issue was water getting into the fuel tanks - a common problem I’m led to understand - but I’ve replaced the fuel filler seals and cleared the crud out of the drain channels so hopefully fixed now.

Once I was able to get some miles under my belt it became clear that there was an issue with the gearbox. When cold all was good, but after just a few miles it would intermittently make a terrible grinding noise, and then a few miles further on the engine would start to stall when pulling up at junctions or lights unless I shifted into neutral. I checked all the obvious stuff like fluid condition and level, kickdown and shifter adjustment, but I quickly exhausted my limited knowledge of auto gearboxes.

Since I wanted to do a manual conversion anyway the car in now up on ramps and the auto box has been banished to the corner of the garage. I should have the manual box installed in the next week or so, depending on how much time I get. I’ll post separately on how that goes.

Cheers
Darren

Back
Back.jpg1683×740 423 KB
Front
Front.jpg1755×702 362 KB
Interior
Interior.jpg1008×756 300 KB

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Welcome,
You have one of the most beautiful production automobiles ever assembled.
Phillip

1 Like
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Looks good, sounds good. Fuel injection parts bolt up, but you’ll need all the wiring for the computer and so on. If you want to make it reliable with FI, we can trade. But there is a large gain in power and more efficiency to be had, and a manual Coupe with 205hp and in that condition…

You can delete the resonators (or was it the mufflers) and get a sharper exhaust. I would not do more.
You can and should use poly bushes for the steering rack. Very easy and also safer.
Bubbles at the c pillar can be bad, yes. Very. But all cars have it anyway.
Adjustable shocks if you want, and don’t mind the paint for now…
Keep it as close to factory as you can while incorporating the changes you want and you have my envy.
Keep us posted, good luck-
David

4

**
Converting to EFI is a fairly large job, Darren - gains little in power, economy and reliability.

If you want more power; triple carbs - or even 6(!) is better. Providing you have experience with carbs…

Frank
xj6 85 Sov Europe (UK/NZ)
**

5

Thanks chaps, I’d like to use the car as much as possible so my desire for EFI is down to reliability and economy rather than performance.

I’d really like some triple Weber style ITBs like Jenveys, but cost may mean I have to initially go with the factory intake system. I’ll use an aftermarket ECU rather than the factory stuff though.

I know XJ Restorations do a suspension kit but I’m having real trouble getting hold of them; emails and voicemail messages have gone unanswered.

Lots to do!

Cheers
Darren

6

Welcome and congratulations on a beautiful car.

Rust at the join of the sill and side panel between the door and rear wheel is the bane of these cars. You will probably find the pans under the rear seat rusted out too.

David

7

Stay with the factory carbs until you have everything together, and should you ever have, do it all at once…
If you search for the SIII’s problems the injection is not the greatest gain to be had in overall performance, common problems like the usual (!) lumpy idle or fueling errors are much harder to get right and even diagnose. And of course you’ll have the car in pieces for weeks if not months: I consider the carbs to be much nicer. If you really want to throw money at it consider a modern AFM, fueling map, solid state ignition, lambda feedback and skip the early days of L-Jetronic.
I think the carbs are decent enough to save the trouble, and if you want to make miles let me tell you that all things considered the fuel is not much of a thing to worry about. Who cares about a few cents per mile. Besides, the manual transmission with a decent top gear will give you the most benefit, the SI with manual, overdrive could do very decent consumption figures, a quarter or so below the SIII with injection and torque converters.

8

Welcome Darren,

good you’ve come across an example with a nice mixture of affordability and driveability!

Your stickshift conversion sounds like a great project - once the torque converter is out your car will feel like 50 hp more, depending on the diff ratio.

As for the steering, poly bushes or the bushes used in the later XJS sportspack are the way to go. Further steps might follow.

Frank has indicated that a conversion to EFI is quite an endeavour. Just remember that the PO who replaced the engine already had a FI engine to begin with - he had a reason to convert to carbs! Engine and engine management are the easy part, once you have a donor. The big efforts come with the fuel return lines to the tanks and the new tanks for the return lines. Again - with a decent donor car on lift next to each other a nice task, but without the lines, fasteners, connectors etc. a real challenge, I’d guess.

David has stated correctly that you’ll get an extra 35 hp, much better fuel economy and easy cold start and running. That being said: an XJ will never be an econobox - I use my car with twin SU’s and auto box at around 15 l/100 km on longer distances (and frankly, a Jaguar’s natural habitat is neither urban nor suburban) - and a standard setup with twin HS8 carbs (not the Strommies) combined with a MOD gearbox will leave a FI car with BW66 gearbox in its exhaust fumes, I’m confident.

Finally, as for the cold start: just try to avoid it:-) The manual choke conversion takes away from the comfort of the AED device, but reduces complexity and is the instrument of choice, if you start your car only once every ten days to cover a considerable distance afterwards. But again, daily early morning rain-or-shine commutes shouldn’t be your standard use of this car.

To check for the substance of the inner sills, just remove the lower part of the rear seat bench. It is only two screws holding it in place and you’ll be able to inspect the floor pan where the rear radius arms are attachedn and the joint of rear wheel arch, sills, floor pan, and over-axle box section. The outer connection of outer sill and wheel arch at the C-post is eaten by the tin worm in most cases.

Good luck

Jochen

75 XJ6L 4.2 auto (UK spec)