Series 1 XJ6 Triple Carb Manual Swap: Car has been sitting a long time... where to start?

Hey Boys! My 911 is back on the road, which opened up a space in the garage for my XJ6!

If you didn’t see my original thread about this thing, here it is.

So anyway, in my 2.5 years of ownership, I have done nothing at all with this, and that’s about to change. This thing sat for I don’t know how long before I bought it, but I did hear it cough/run on starting fluid before purchasing.

So full disclosure, feeling a bit overwhelmed and intimidated by this, because there is just so much I don’t know about this thing, and the… ahem… wiring.

The purpose of this post is to discuss what I should do first, and how I should dig into this thing? I NEED to do the fuel system on this, have carb rebuild kits, filter, etc. Also have valve cover gaskets and stuff since these are seeping. Plan is to get it running/driving and cleaned up a bit and go from there.

Here is my current plan, but I am open to suggestions:

  1. Drain oil, change filter, refill w fresh 20w50
  2. Drain old fuel (not sure how to do this with two tanks)
  3. Change fuel filter and spark plugs, throw some marvel mystery oil in there to help lube rings/soak
  4. Remove carbs and intake manifold (all super gross, carbs are not working correctly)
  5. Rebuild carbs
  6. Cerakote intake manifold
  7. Pull valve covers, fix cosmetics
  8. Adjust valves
  9. Reinstall, turn key, see what happens

Any other basic advice for plan of attack here? Do things in different order? Stuff I am missing? Appreciate the advice!

there’s no real order in what to do, long as all gets done, i wouldn’t bother about valves adjust until you hear it running (unless you suspect something) draining fuel> if tanks are fairly full then just use the electric pump (ignition coil disconnected) fuel drums up front and pump till most is out, then undo the drain plugs on the bottom of the tanks with a pan to catch last bit of fuel…if you just want to get it running then the basics are > fuel & filter - carbs- oil -filter - spark plugs - ignition system - check gearbox oil/fluid - cooling system flush (garden hose is enough) i can help you with electrics if need be.

Good advice from Tom

be aware that on most older unused XJ and other IRS Jags with inboard rear brakes that there is a high chance the rear pistons are seized in the calipers

This isnt the end of the world if the fronts are ok, the next one is “end of world”

I remember a guy restored his Jag at great expense, did everything but left the brakes till last, I meant to tell him not to do that.

It is especially important the Master Cylinder is good, as most failure modes allow the pedal to go to the floor and thats what happened to him, with disastrous results (and me with, lucky no car in front)

Summary of that advice is unless you have evidence or feel very confident about the Master Cylinder having had it seals renewed in the last 20 years, in my opinion, the Master Cyl should be removed, inspected by a brake expert and sleeved in SS, unless he says you do not need this and new seals.

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I was there about 2.5 years ago. I knew nothing about cars and less about jags. If I were you I would try to get the engine running as is just to see what you are working with. If you have a cheap endoskop for a cellphone that comes in handy to look at the cylinders.

The fuel system is always an potential issue. I would skip it altogether and wire up the pump in and back to a canister of fresh fuel just to take out the whole fuel system problems. You can deal with that later.

Rotate the engine by hand first to not bend any valves… ask me how I know. Add a little bit of oil to each cylinder first. See if you have spark on the plugs and give her a go.

I did this to an S2 with carbs while I was looking for a donor engine for my car and was able to get that engine running in about 2 hours. It wasn’t smooth or anything but it ran… I did a compression check after that and realized that one of the cylinder was very low.

Anyway if you confirm fuel, and spark it should start especially with a carb. engine.

I Whole Heartedly Agree with Max…get it running…to add…you can gravity feed the carbs via a funnel shoved into a hose then smaller hose and maybe smaller hose and connect to the feed pipe of the carbs…fit a bracket to hold above engine (I duc tape the harbor freight funnel to the windshield running the hose configuration under a windshield wiper and onto…connected to the carb pipe…tap the carbs with a hammer a few times to help open the needle and seat…and see if it runs

Special note: nobody stops driving a car that runs…nobody…Therefore, all “barn finds” have some catastrophe that happened…something is wrong…that is why the car went unused

…make the engine run first…

ps. Max is correct…
Also…side draft carbs (what you have) will NOT start unless choked…or starting fluid/gas squirted into carb throat

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As an interesting side note, in the US we have 2 well known hydraulic rebuilders/sleevers (on the East Coast anyway) Apple Hydraulics and White Post. I needed to have the masters rebuilt for my 140, so I was looking into this a couple months ago…

White Post only does brass sleeves. Apple will do SS or Brass.

I asked Apple what their input was on doing the SS vs Brass, and they sent the following:

“Our take on brass vs. stainless: If car is driven every month or two, go
with brass. As you drive, fluid heats up and moisture evaporates, so you
don’t need stainless part and you don’t want steel part. No matter how
machined, steel surface is harder on rubbers, more abrasive than brass.
For example, telescopic shock absorbers have rods that move back and
forth through stationary seals. These rods are not naked stainless
steel, they are chrome plated and highly polished. This is also why
steel was never used to make brake cylinders - castings are either cast
iron or aluminum. We recommend stainless sleeve only for rarely used
cars, so called “trailer queens”.”

  • Drain oil, change filter, refill w fresh 20w50


  • Drain old fuel (not sure how to do this with two tanks)

Yes, as mentioned above you can probably use the fuel pumps for this. Also, check the condition of the inside of the tanks, they can get pretty gross.

  • Change fuel filter and spark plugs, throw some marvel mystery oil in there to help lube rings/soak
  • Fuel filter definitely
  • Spark plugs, maybe?
  • No idea on MMO, I’ve not heard of that one, but it may be good…
  • Depending what type of ignition this car has, check plug wires, distributor cap, rotor, points, timing etc
  • Remove carbs and intake manifold (all super gross, carbs are not working correctly)
    Assuming you have SU, since you mention triple carb, get your kits from Joe Curto
    He will also do a full rebuild for you if you want to spend the $ and know it’s done right and looks good.
  • Cerakote intake manifold
    Interesting idea, I’ve never heard of this, but should work
  • Pull valve covers, fix cosmetics
  • Adjust valves
  • Reinstall, turn key, see what happens

Adjusting valves requires cam removal which could end up being a bigger job than hoped for, I’d put that off unless you really think they’re off.


everything said so far is true; while there may be some cars that just stopped running because their owners weren’t able to drive them any more, most of them are sitting and/or relocated to barns etc, because the cars had issues. On series Jags in the US I’d guess 80 % of such victims have to be attributed to the fuel system or to a shot head gasket.

So, yes: checking the engine has priority, but drain the tanks and feed one (checked!) functioning pump with fresh fuel. Before you even dare to turn the key make sure the engine is free. The spark plugs are presented to you on a silver tray. Undo them carefully (the head is aluminium), if necessary with some Caramba or similar product. Then peek inside to check for water puddles or rust. Then pour in a teaspoon of oil, let soak and turn over the engine without the plugs in place just by hand and stop at any sign of resistance.

The one thing I’d add is that inspection thing: try to find out as much as possible about the car before you get in too deep. Everything that has a function should function. Check all the rubbers, bushings, seals, gaskets that are accessible. Make a list and take pictures. Be honest to yourself: it is true that spare parts for series Jags are cheap compared to Porsche spares, but there are many. From your pics I would guess that only the used consumables will amount to a grand at least. Most notably, check out the body: while even a spare engine can be had and installed at reasonable price and effort, an overly rusty hull will cost you the equivalent of your kid’s yearly college fee: rear valance and quarter panels are easy, front wings are doable, but front and rear window frames, inner and outer sills, floor, A and C pillar require quite some MIG skills. Check the area around the rear radius arms mountings (close to where the car jack mounts before the rear wheels) - if this area suffers from severe rust it will be hard to keep the patient alive. It is no big deal to remove the rear seat bench. That will show you pretty well the state of the structure around the rear axle.

Good luck and keep us posted


75 XJ6L 4

Actually, the brakes feel AWESOME in this car. Ever since I rolled it out of the storage shed a few years ago, til last weekend, I’ve rolled the car off trailers and into and out of garages and I’m always impressed with the pedal feel, it feels like a modern car. Wild. I’ll be sure to dive into them before driving it, but right now I want to focus on getting it running.

One other thing, the previous owner sold this as a running driving car, but when he sold it it had been sitting inside a storage unit for a while, and wouldn’t start which he was surprised about. It cranked fine, and a lot of the electronics seemed to function, so I sprayed a bit of starting fluid into the intake near the carbs and heard it run briefly, so I’m assuming there is nothing too catastrophic about this thing, I really think it was just parked too long, and the carbs most likely need to be redone.

Draining the fuel tanks is essential, they have either a 13/16" brass filter plug, and if you are lucky, a 9/16" drain plug in that

The big filter plug is often seized in the threads

Ideally they should come out, the filter mesh be inspected, and anti-seize added to threads. You will need new rubber washer seals if you do this

If you have a S1, they have a special way to fit the boot filter element, check the archives, or it will bypass !

take off the carb assemblies

flush the fuel line with the pumps into a bucket

often the carbs can just be taken apart, cleaned and inspected, put back together, tuned and be good, but you do need new bowl lid and carb to gaskets

As to the diaphragm and other parts they will often be ok, dont know your intentions, as you mention triple carbs

I have setup a manual choke triple HS8 on 420G manifold to fit, but I can advise that in my opinion, triple SU offers no discernible performance benefit, complicates tuning and idle

twin 2" SU provides sufficient airflow, better at low to mid. I would presume they might be helpful above 4500RPM, but few off us would use our engines that way

I’ll be draining the as soon as I can get the car up on jackstands, as it seems my quickjack isn’t long enough to work with this chassis.

Not sure about the special way to fit the filter, I did grab the S1 filter tho, which is differen than S2 or S3.

Yeah, but triple SU + manual trans is what makes this thing so cool imho. As far as I know, the difference between the XJ6 and the E type 4.2 was triple carbs and ??? but the HP rating went from 245 to 265hp, and considering the carbs/intake on this are worth about what I paid for the car, I’m going to run them. I have 3 rebuild kits I grabbed from Terry’s Jag/Engel Imports, rebuilding them is definitely on the agenda. I’ve rebuilt a lot of carbs so I’m hoping these are relatively straightforward.

Ok, you already have the triple SU fitted, nice

Rebuilding them is easy

check the archives using Peter Crespin as author and fuel filter as the term and he instructs regarding the filter

In respect to HP, as you know, 2 things. The quoted HP are not realistic, and as I mentioned, max HP is always at high RPM, so not usually where the engine is at, but still :slightly_smiling_face:

You dont need to even lift the vehicle to drain the tanks, although it probably is easier

Be careful not to round the brass 13/16 head, or even worse, tear the tank sheetmetal

Indeed, Rob - the triple carb set-up is the most powerful factory version. You haev a gem!

Do a compression test - it will confirm if the engine itself requires lttle further actions. An oil change is mandatory before serious running - it may or may not run o the old fuel, but changing it may be required. Running may show some carb attention is required - and there sure will be problems in other areas showing up in due time…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

Alright boys, gave up on the leakdown tester as I wasn’t able to stop the pressure from just rotating the crank and then not sealing, so I made the pivot to a compression test. You can watch the video here, if you want to see more:

Basically, the first time I did it, I got (cylinders 1-6): 110, 110, 90, 110, 110, 90. Not great, would really like them to be more even. This car only has 79k miles so I was expecting way higher numbers. This was sort of dry, I had put some marvel mystery oil down the plug holes a few days prior. At the end of this video, I threw some MMO down cylinders 3/6 and got 125, which is better, but from what I’ve been reading, this should be more like 150psi???

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Not sure what the “should be” but mine are 135-140 and mine matches all the book specs in terms of performance. Sure mine are closer to each other but maybe you just need to drive it. YMMV.


the low level may also be a consequence of the technique applied (duration of cranking) and the accuracy of the tool. Even if the figures are a bit low, they may come up with regular use of the car, as Max wrote.

More important than absolute values is evenness and - while some +/- 10 % are typically deemed tolerable, I’m a bit surprised at the distribution with either the same 110 (four times) or 90 (twice). Are you sure your compression tester is working correctly?

But, hey, it looks like your engine is free and the cams and valves are doing what they are supposed to! That’s a great finding in itself. Now you can address fuel supply issues and finally get those triple carbs going again.

Good luck


75 XJ6L 4.2 auto (UK spec)

Just make sure that when you are quoting cylinder numbers that you are aware #1 cylinder is actually at the firewall not the radiator.

there is a few ways to stop the crank rotating, one of the easiest involves fitting a spanner or socket on one of the 4 bolts that hold the pulleys on the damper, or the main crank bolt itself

I second Jochen, Rob - procedure is important, and your evenness is well within the 15% limit, but your compression is low.

Verify procedure; floor the pedal and crank for 4 seconds - if pedal is not floored, compression will read lower… The compression pressure will naturally vary with the compression ratio - 135 psi at 9:1…

Also, with low compression; add a spoon of engine oil immediately before testing each cylinder - the ‘wet’ test.
The oil will seal bore leakage - and the raise in compression reading is an indication of bore/ring wear

xj6 85 Sov Europe (UK/NZ)

Good to see you here with an update, I was wondering what happened considering how old the second Youtube was. I’m in the same position, brought my '73 home 2 days ago.