Hello everyone, I'm new to the forums, although I have been lurking for a while without an account. I figured it was time to introduce myself and hopefully share some knowledge that I have learned the hard way.

I'm Max, and I've been a lifelong Jag enthusiast.

A few months ago, I spun the rod bearings on my 1999 XJR's factory nikasil engine, a previous owner had done the timing chain guides but did not bother to clean the pieces of old guides out of the oil pan, clogging the oil pickup and starving the rod bearings of oil. I found that it was easier to find a used 4.2 engine in good condition, and for a reasonable price, so I decided to do the swap. There is a little bit of info online about modifying the upper oil pan and the like, so I figured it would be a fairly straightforward swap. Not so.

I am going to try to lay this out in such a way that it will be useful for anyone who wants to do this in the future.

I re-used as many parts from the blown 4.0 (AJ26s) as possible- Partially because of time considerations, and partially because i'm a cheapskate.

Parts that were needed from the 4.2:

• Short block
• Oil pump
• Oil pickup tube

Parts that were needed from the 4.0 that are of particular importance:

• Upper and lower oil pan. As many other guides have mentioned, the upper oil pain will need to have a piece of webbing cut away to create clearance for the oil pickup tube. You cannot use the 4.0 oil pickup tube, the 4.2 oil pump is larger and better, and does not draw oil from the same cast boss in the upper oil pan as the 4.0 does. If you inadvertently use the 4.0 pickup, your engine will not be able to draw oil into the bearings and will very quickly be destroyed.
• Timing cover. The AJ33s timing cover that my engine came with had to have some extra material removed to clear the power steering pump and A/C compressor on my XJ. Re-using the original 4.0 timing cover avoids having to do this work.
• Camshaft Indicator (reluctor.) if your car started with an AJ26s, and not an AJ27, the toothed piece on the end of the driver's side intake camshaft will need to be transplanted to the new engine in order to preserve the cam sensor signal that the Denso computer is expecting. To do this requires you remove the camshafts from both the old and new engine, center drill, tap, and use a slide hammer to extract both indicators, and then use an arbor or hydraulic press to reinstall the 4.0 (AJ26s) cam indicator into the 4.2(AJ33s) cam. If you don't care about the old 4.0 cam, you can cut it in half in a band saw and hammer the indicator out with a long rod. You will need to re-time the engine. You can buy the tool for timing all Jaguar V8s which is readily available, or you can make it from aluminum bar stock if you are handy. Torque the cam sprockets to spec and make sure they hold time after a few rotations. Another important note here, when installing the camshaft position sensor: you may need to trim down the length of the bolt that retains it, as well as the one on the valve cover so that it does not interfere and damage the sensor.
• Lower intake manifolds. The AJ33s cylinder heads have a slightly different port shape, and not all the holes line up. There is enough extra material to drill and tap the holes that are needed. You will need a metric M6x1 tap, if memory serves. Confirm with a thread gauge and the bolts you removed from the old engine. The way I did it was to bolt up the two bolts per manifold that do line up, and then use the manifolds as a guide to drill and tap the holes. Using the aj26s lower intake manifold gaskets from Jaguar, I put a very thin layer of motoseal on them and torqued them to spec.
• Fuel Rail and Injectors. Due to the change in location a few mm further back of the lower intake manifolds when installed on an AJ33s, you may need to clearance the fuel rail with the cam position sensor on the driver's side cylinder head. Do not force the fuel rail into position; it will snap, and you will be embarrassed and have to order a new one from your favorite junkyard, or if particularly desperate, from JLR for $800. I accomplished this clearance by using sandpaper and a file to slowly remove material from the cam position sensor as well as the side of the fuel rail until there was approximately 1mm of free clearance to prevent any forces from acting on the rail when installed. You can remove a suprisingly large amount of material from the cam position sensor with no ill effects.
• Knock Sensors. I used the updated AJ33s style knock sensors because i received them in excellent condition and they are a better design and more durable than the original AJ26s units. Either will work.
• Intercoolers. Similarly as stated before, the intercoolers will be a few millimeters further back once installed. This can make it difficult to install the two hoses that connect the elbow intake to the supercharger. I found it best to install one intercooler, then the elbow, then the other intercooler on top of it for the easiest fit.
• Supercharger. No modifications necessary. Now is a good time to change the supercharger oil and fit an undersize pulley, if the mood strikes!
• Supercharger intake elbow. Total pain to install. Pry carefully and methodically, and be careful not to crossthread the bolts that hold it to the supercharger.
• Throttle body. Bolt it back up, should fit right in. Now is a good time to replace all the broken and perished vacuum lines that like to crack upon removal.
• Supercharger outlet plate (says "V8" on it.) Needless to say, I think we are all aware of the technical service bulletin related to these pipes. Doing this swap will only make that condition worse, because the supercharger location does not change while the intercoolers move back a couple millimeters. I do not represent this to be the best solution, but the way I solved it was by super gluing thick fel-pro cork gasket to the ends of each side to make up the extra space to prevent the pipes from coming out of their holders. I am unsure if oversize hoses are available, but if anyone wants to make them I would pay a pretty penny for them.
• Cam covers. Re-use the original 4.0 cam covers.
• Coil packs. Re-use the original 4.0 coil packs. Highly recommend only using original quality DENSO brand coil packs.
• Miscellaneous intake piping. Re-use your original piping.
• Crank Pulley. I have been told the 4.2 crank pulley will work. I did not have it, so I did not use it. the 4.0 one will work on the 4.2.
• Engine Accessories. They all bolt right up.
• Coolant neck/Thermostat housing. Re-use the 4.0 one. Get the upgraded housing made of aluminum. Supercharger goes on first!
• Exhaust Manifolds. Re-use the 4.0 ones.

Installing the engine is fairly straightforward, in fact I would consider it relatively easy due to the good amount of space to work in the X308 engine compartment. General tips include making sure the torque converter has fully engaged the pump on your 722.6 otherwise you will not be able to get the engine to mate right with the transmission. This is most easily accomplished by squatting in the engine compartment and wiggling the torque converter until it only sits about 1cm proud of the bellhousing.

I'd also like to mention that doing this swap was significantly cheaper for me than trying to buy an AJ26s in good condition, and has noticeably boosted the car's already formidable performance.



Engine compartment sans engine

New (Used) AJ33s

Side by side

Complete (Almost!)

 

you got some pics of your cut off timing cover?

i’m slapping an aj34 from an xkr in and i’m doing it the laziest way possible. either gonna use the xk’s high pressure line to the rack or mount the old pump in

 

Nice work and nice writeup. To my eye, intake elbow is not pushed back few millemeters. More like couple centimeters.

 

if I were you, I'd just bite the bullet and use the 4.0 timing cover. I had to remove a lot of material to get the AJ33 one to work. Basically you have to remove all the extra "flashing" on the drivers side.

 

didn't need to do it. xj power steering line was still screwed into the old pump adapter, once i separated them i got a line that fits the 4.2 pump.

 

The AJ34 has the same upper sump and pan arrangement as the AJ26 and AJ27.
The LATE AJ27 (from engine 0108130000) has the same upper sump and oil pump as the AJ34 because the XK8/R X100 body/frame did not change much 1997 to 2006.
The AJ33 is fitted to the X350 and X202 onward so sump is completely different.

 

So let me clarify, my AJ33s was from an S Type - it had a different upper sump than my '99 AJ26s, so I had to swap it over. It had a different oil filter location and it eschewed the oil cooler.

 

CORRECT

The AJ33 was used in the S-Type and X350 sedans hence the different pan and oil filter location.
The AJ34 will drop right into the X308 and X100 frame mounts.

 

job done, all shortcuts taken. supercharger stayed on. cam reluctor not swapped. you can do this in 2 days if you really get a move on

you can keep the 4.2 cover and power steering pump. the old line has too few threads so you need to take the old adapter fitting out of your power steering pump (big 24mm nut) and thread it into the new ps pump with an M16 crush washer.

AJ34 upper oil pan doesn’t have lower 2 holes threaded because they go backwards onto the 6ZF. bolt and nut works fine. everything else has been explained before

 

Great job!!! Glad you are back on the road.