Quick Reference: Swap your 4.0 block with a 4.2
 

Base AJ26/AJ27 car:

SC Cars (SC= Supercharged)
-Any 4.2 SC engine can be used, Stype, XKR, XJR, XF and Range Rover, though the latter needs some extra work, see note below.
-Use only the base block, so the Lower end/Base Block, heads, timing gear, camshafts, oil pump and maybe the supercharger.

Then re-use from your 4.0 block:
-Front cover
-Front lower pulley
-All electronics (Ignition coils/Fuel injectors etc)
-Fuel rail/intake manifold
-For the AJ26 the camshaft positioning indicator (that one sits on the Bank A, Intake camshaft), and flywheel
-Lower sump
-Cam covers
-Camshafts (but only if the 4.2 block had VVT).

Modifications needed:
-Bolt holes from Intake manifold do not line up, when counting from the front, numbers 2 and 4 fit, and new tapered holes need to be made in the heads for 1 3 and 5 (easy). Then port the intake manifold to ensure good alignment with the intake ports of the head.
-The oil pickup is different with the 4.2 oil pump; you need to modify the original sump to allow space for the new pickup. This is important as the 4.2 engine uses piston oil jets to cool down the system (This is also why the 4.2 blocks do have not the issue with short running that washes away the oil film…).
-Camshafts, you can use the 4.2 camshafts without issues if it was a non-VVT one, but you need then to exchange the camshaft indicator (AJ26 only). The AJ26 has 1 vane, whereas the AJ27/33/34 has 4. This saves in changing the valve clearance and everything will fit as it should have been.
- If using the 4.2 supercharger, you als need to use the 4.2 SC to intake elbow gasket, and modify your intake elbow a bit where the bearings form the SC stick out, 1/2mm should be milled away.

Optional: Use of the 4.2 fuel injectors
-The 4.2 injectors are better; they have 12 fine openings giving a much better fuel atomization. There is no need for an ECU Tune they will work directly. The later 4.2 engines (at least those with VVT) have brownish injectors which flow about 10% more, then the blue 4.2 injectors, and the latter also flow a little more again then the 4.0 ones (not much though). The impedance is slightly different from the 4.0 ones, but they are all high impedance injectors. If the original engine was from a Jaguar XKR 4.2, and this project is for a 4.0 XKR/XJR, you can reuse all, so intake manifolds, fuel rails/injectors and intercoolers, and if you have it also the inlet fuel hose (straight fit). You only need to bolt on a return line where the fuel temp is located, no welding needed. Also the injector rail electrical connecter needs to be swapped (so some soldering required).

However, if the 4.2 engine was from another car (ie Stype/XF/RR/4.2 XJR), you need to modify the fuel rail inlet (welding required), and you need to find the 4.2 XKR intercoolers, as your old will not fit the new manifolds. Not sure if it is worth the effort than.

For the pioneers:
-Use the AJ26 camshafts (only when you come from a AJ26, not AJ27), the AJ33/34 (4.2 engines) seem to have a similar camshaft profile (more info from Count Iblis in the responses) This saves the trouble to exchange the camshaft indicator.

General comments:
As it is easier to take the heads off to make the new holes, better to buy new head gaskets and head bolts. The latter are stretch type and can be used only once!

The 4.2 block has some strong advatanges (especially for those that are looking for some more power), besides the bigger stroke, you get forged pistons and piston cooling via oil jets (crankshaft is still cast instead of forged). The so called beter combustion chamber with a good squish area, seems to be not so good afterall.

Note: Extra Engine adjustments for a Range Rover 4.2 Block
- Both Engine mounts on the block need to be grinded of about 7 to 8mm
- Oil dipstick hole needs to be drilled thru (easy to see)
- 3 bolts for the triangle pulley holder are M8, so either use M8 bolts when you re-use also the front cover, or helicoil the holes in the block to M6
- Coolant hole (for EGR and TB) just behind the Starter isn’t drilled and tapped.
- 1 bolt hole for the starter isn’t threaded, and also at the same position the gearbox bolt isn’t threaded either, can be helicoiled.
- When re-using the oil pump of the 4.2 (recommended) you need a Jaguar 4.2 oil pickup
- 2 bolt holes are missing on the block for the steering pump bracket. So they need to be welded on.

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NA Engines (NA = Naturally (or Normally) Aspirated)
I have no direct experience with these; however most of the above will apply, unless stated below.
Again any 4.2 NA base engine will do, from an Stype, XK, XJ and XF and Range Rover (but not the pre 2006 engines as they where BMW originates), The Jaguar 4.4 engine used in the RR can be swapped again, so that would be a nice 10% gain ;-).

Possibly the 3.9 ltr 2003 and up Lincoln LS and Thunderbird engines as these are also based on the AJ33/34 4.2 engine from Jaguar stroked down from 4.2 to 3.9 and now with VVT. But I am not 100% sure as I see some small differences on pictures to where the AC is mounted to the block for instance.

As there are small variations in VVT systems between the AJ28/33/34 (and Lincoln/thunderbird), I would strongly advise to keep the 4.0 Camshaft/Timing gearing, that can be swapped.

What makes it more difficult for me to judge, is that the 4.0 engines use a plastic intake manifold, and I am not sure how much material is there to shave of to ensure nice mating to the intake holes on the head. Though it should be possible imho.

Also I don't have info if one could reuse the 4.2 injectors as for the SC cars mentioned above.

Swapping a 3.9 NA engine from Lincoln (pre 2003)
Another option is the older 2000-2002 3.9 ltr engine from the Lincoln LS. You might be able to reuse some parts, however to be sure, best to reuse all the parts as suggested above. Here you do not need to make any manifold modifications as far as I am aware, so it will be an easier swap. You also do not need to replace the oil pump pickup, so no extra work there, but you need to reuse the 4.0 oil pump. This engine does not have VVT, so you need to swap the camshafts/VVT gear.
There can be some similiarties to the range Rover block as mentioned above for the SC engines, so be prepared for some extra work there.

For everything above
Please note that all of the above is specialist work, but that speaks for itself I think. It is not rocket science, so it is all doable for the seasoned mechanic.

Andre,

Thank you very much for posting this information. I knew it was out there after reading that Racing Green was performing this swap, but I had not been able to find it.

In all of the time I have wasted on forums for the past several years, just about the only factual information of any significance I have learned has come from you. I appreciate your willingness to exchange information, and have always hoped that sharing what I know with others will provide them with solutions and return me some benefit in the long run. Today is a good day.

Since I know that you have a bit of an entrepreneurial spirit, my first read of your description gives the idea that manufacturing a modified intake manifold with matched mounting locations and intake ports for a direct bolt-on to the 4.2 heads would be a great idea.

I am assuming that this interchange has been successfully done and proven as reliable? Some of the questions in my mind centered around the different fuel, ignition and camshaft advance mapping that might be required when using all of the 4.0 engine control components on an engine with larger cylinder volume, different compression ratio, and different combustion chamber shape.

If you're telling me that those concerns are not sufficient to exceed the capabilities of the stock 4.0 engine management, then I'd say it's time to start swapping. I'm left to now assume that the stock 4.0 MAFS and ECM have the "room" to read and compensate for the differences. Please straighten me out if I have any of this wrong.

It might help if you could go through your post and make sure you have worded everything the way you intended, I am a little confused but you relayed the basics very well. Lord knows if I had to write in a second language, I wouldn't be able to write at all.

NICE JOB. THANK YOU !

Thanks for the kind words, and I would agree this is good info, has also taken some time for me to get (and validate/pioneer)

The existing 4.0 manifolds can be easily adjusted to mate right; making new ones might be expensive, but an idea.

All is proven, no worries, have done one myself, and am working on another now, and this is besides many others who have done it.

Have updated the text above now, please let me know what could be unclear, so I can update.

I think the changes to the Lincoln engines are minimal/not noticable, if you see how extreme one can play with the SC cars I believe for sure that there is enough room for it even including the larger 4.2 NA engines.

Andre.

How much would AJ27S aprox cost?

In October, I picked up an AJ27S from a 2000 XJR with 41K miles for $2,100 (USD) plus $125 shipping, no core charge/requirement. That was the least expensive I found; most good used engines were in the $3,000 range, rebuilt/remanufactured in the $5,000 range, and new around $8,000 plus. The only part missing from mine was the throttle body, which was fine because I had to use my AJ26 throttle body anyway, but whether the engine comes with the s/c and charge coolers or other accessories like water pump, etc. may affect up-front cost as well as cost of the labor for the swap.

Thanks for that!

Hello,
as I understand - I can swap 4.0 for 4.2 in 1999 XK8 and manifolds and electronics will be compatible. I can get a complete engine from a junkyard only without accessories (intake manifold and injectors are included...

The electronics are really just plug and play? Wouldn't the ECU need reprogramming/remapping at least?

Electronics are NOT compatible, so you need to re-use the 4.0 parts as described.

But as said in the NA section, I am not sure how well you can mate the plastic intake manifold. As I don't have one (am more than willing to check one, but then some must send me an intake), I can't give a definitive answer on how well you can mate it.

As you re-use your electronics, there is no need for a ECU reprogramming. Even not the small increase in engine volume.

Will the linclon LS engine bolt right up to the tranny?

I don't get it. Why would you want to *******ise a car that way? I'd maybe understand better if the swap resulted in a bigger engine, not smaller.

It reminds me of a guy that wanted to put a chevvy engine into a Ferrari. He really missed the whole point of what makes a Ferrari what it is.

I KNOW I KNOW:icon_hyper: TEMPRAMENTAL AND EXPENSIVE :icon_wink:

Lol. Except you just described my XKR. Its not half as reliable or cheap to maintain as my Ferrari 308 GTS was.

I want to *******ize the car because I can't find the proper engine. Give me a good deal on a low milage 4 liter and I would be happy to buy it. Putting a Ford LS engine into it would not be *******izing it. It is putting the same engine back into it just with a different name tag. I worked in Ford engine plants for 30 years and know that different engines are pretty much the same except for the decal they put on it. I also have a 57 Rolls that came without an engine and no interior. To bring it up to original RR standards it would cost me $60,000 and if I wanted to sell it after I could get $30,000. So tell me if it is practical to use a Ford engine in it or should I just scrap the car? *******izing has a place in this world.

I'm putting a Ford V8 into a 28 year old Volvo just because it feels good.

My religious mantra:

'If it feels good, do it!'

OK then, I'm thinking about putting a Harley 80 inch V-twin on my lawnmower just because it feels bad! Ha, ha!...finally, something to do with that old Harley.

I want to see the mower when you get it finished. Video post on U Tube will be cool!!

Now we are getting somewhere. Its okay to want to do the job right but sometimes ya gotta work with what ya got or you will never get anywhere. Chevy in a volvo, great. Harly on a lawnmower now we're talkin.

great info up there! im a little confused with the 3.9 swap tho, what is the reason for replacing the oil pump? and how does the LS 3.9 fit in with all the electronics? i know the ls and stypes use different protocols in their computers so not sure how that would work, on the other hand if you reused all of your old sensors and all other electronic components mounted on a 3.9 they should be ok?

Ifim not mistaken the 3.9 Ls motor and the jag 4.0 have exactly the same displacement, I think 3345cc or something like that except jag rounded it up and ls down