What improvements where made to the 4.2 engine compared to 4.0? Like forged pistons, stronger bottom end and so on. Many have done a conversion from 4.0 to 4.2 but what are the advantages besides the obvious increase in displacement

A 4.0 engine can of course have forged pistons when rebuilt. So when my 4.0 engine eventually is worn out, what option should I go for if I also want to upgrade to a higher spec?

Regards,
Higgins

 

"So when my 4.0 engine eventually is worn out, what option should I go for if I also want to upgrade to a higher spec"?

A later model car.

 

Thanks for the suggestion. But that will most likely not be my choice, I like the idea of upgrading the car bit by bit

 

My sincere understanding is that it's frustratingly hard (borderline impossible) to upgrade the 4.0 NA engines in any non-trivial way without serious downstream communication issues. As a 4.0 owner, I would love if this were not the case, as I find the power a bit underwhelming. You can certainly make them more reliable though.

The 4.2 engines sorted out some of the fatal issues of the 4.0, including the timing chain tensioners and guides, as well as doing away with Nikasil cylinder lining. The supercharged engines can be toyed with a bit more (some here have pushed their XKRs to over 600 hp). They are much more reliable/stout units out of the box. However, as you may have seen from this forum, swapping to a 4.2 is probably just as costly when accounting for time/labor as just buying a newer X100, which is something many of us (myself included--very attached to my car) see as an unattractive option.

 

it would help if you had any particular complaints about the 4.0 that can be put to words. in this manner we can tell you what to expect and also if the basic design is the limiting factor. if you have a 4.0 car, you can do an LS motor conversion and really take the car different places, even manual trans. see Jaguar Specialties for this option. to my knowledge the 4.2 is not actually more stout in terms of hardware. it is more of a gradual refinement. some have even installed a 4.2 in a 4.0 car with few issues, but you must use your electrics and fuel delivery system. the 4.0 has a major benefit of smoothness being a square engine whereas the 4.2 has increased drive-ability and better mid range. you might thus appreciate an XKR with the 4.0 as this is considered by some the best of both worlds. if you really like your car as is and are just concerned with quality and longevity, when it is time simply have Jasper rebuild your engine. few will do a better job and they often can add bespoke upgrades during the process. i have not investigated these options for our engine. if and when mine needs to be rebuilt, they will do the job to OEM spec.

so, give us an idea what you are looking for and many here can guide you accordingly.

 

I forgot to mention my car is a Xkr 4.0. And like many owners I love the smoothness, but would also like a bit more power. Ls conversion would not be an option for my since the car then no longer is a jaguar in my eyes, I want to keep it a true jaguar.

After reading a lot of threads here I reckon that the supercharger can be spun faster to get more power, especially mid range. But I also reckon that more heat will be produced, and that 4.0 has got cast piston but 4.2 has forged pistons, and the latter can take a lot more heat.

That brings me to the question, what more improvements were done to the 4.2 engine compared to 4.0 (Xkr)?

Regards,
Higgins

 

You could be disappointed at the difference between a 4.0 litre and a 4.2 litre with only an engine update.

The differences in the models wasn't simply increased capacity - it was part of number of upgrades to transmission, suspension and brakes. Jaguar claimed an 8% improvement in performance between the 4.0 and 4.2 but only 3.5% of this was attributed to the engine.

Having had both a 2001 4.0 and a 2005 4.2, I didn't find the difference all that noticeable. Certainly nowhere like the difference between an XK 4.2 and an XK 5.0.

Graham

 

the very modest amount of extra heat, produced by upgrading the S/C will not be of any consequence to the 4.0 cast pistons. Piston failures generally, and specifically in the 4,0 are very rare, A slight to modest increase in blower pressure is going to be well within the design limits of the 4.0 cast pistons. Only when you are 2X or 2X+ the boost levels, will the need for stronger pistons be a prudent step.

Installing a 4.2 motor is really a money pit that won't get you a kick-in-the-pants uptick in power, which it sounds like that is what you are after. Just work with the motor you already have, A better S/C ratio is a good place to start. Then talk about a water injection system to go to another level. BCPrice36 is the one to PM on this forum for that info.

Z

 

Except of course those issues were already sorted out on the 4.0 engines at the end. Steel cylinder linings replaced Nikasil in 1999 and the latest timing chain tensioners and guides were being used on the last of the 4.0 engines. The 4.2 wasn't some huge leap in reliability over the 4.0, just a culmination of all the other improvements Jaguar made every year to the 4.0 engine.

 

Thanks for your thoughts on this. If I summarize the inputs and merge it with my vision, the output will be as follows. I will stick to my 4.0, modify if step by step until it brakes down 💥😵😋

Then I will have it rebuilt, most likely with forged pistons and rods as well as other upgrades like bigger s/c.

So far I have focussed on upgrades to the suspention and brakes with lowering springs, new bushings and ball joints, brembo brake conversion. Only upgrades so far affecting power are stainless exhaust from Milltek and a intake tube from Mina Gallery

Now I will order smaller upper s/c pulley as a start

 

Reads like a plan, but I wouldn't take your approach. Forged pistons, stronger rods, and crankshaft, main and rod bearings will all have to be custom made. Suppliers only carry OEM parts. If your crank journals are out of spec from the very limited size OEM bearings, then you need to get the crank journals built up and ground to fit the stock bearings. I doubt if more than 10 forum members with AJ-V8 engines have rebuilt them for performance. Due to this low volume, everyone has had to have their parts custom fabricated. Once you go down this route it costs a lot of money, and more importantly, lots of patience and time. Expect up to a year to build up your dream engine if you do it yourself and at least 6 months if you pay someone to build it.

If you are rebuilding the engine other than a stock rebuild, you should spend a couple thousand on a rebuildable complete engine core and build up the new engine while your car is still running. Then when your engine dies, you can swap in the new engine and have a lot less down time. (During the build time of your new engine, you can plan for the electrical differences between your old and new engine.)
To rebuild the engine correctly you should plan on a minimum of $6K (USD) and more likely $10K to $12K if you are planning to put on a KB supercharger. It will be a lot of work because there isn't a template on what is the best rebuild approach. (The AJ-V8s don't have the aftermarket support like LS series GM engines.)
Most owners of our cars realize how much work, time and money it will take and either purchase another car or drop in another used engine or stock refreshed engine.
Economics is a big factor. Do you want to put $10K into a car that is worth only $7K to $10K ? (You have to really love that car!)

If you are serious about eventual mods on your car, I would start by searching and reading all the postings for engine rebuilds on the jaguar forum. There are a lot of details here. You will learn a lot and perhaps change your plans.

Ask Deuce2000 about the engine he has been building.. (He is perhaps the 5th person on the forum to discuss and publish what he is doing to his engine.

Good luck.

 

You meen things like the 4.2 is hard to kill, doesnt have timing chain tensioner issues or drop exhaust valve seats out of the heads when run hot. Etc???? Those kind of things

 

Clearly we have different views on this topic.. as always. I guess few people in this forum actually ever worked as engineers at Jaguar or even as a jag engine mechanic. But all inputs are appriciated. Keep'em coming 🏁😋

 

Sounds a fun project and as others have mentioned will take a lot of effort & money - so good luck if you go ahead.

Did the 4.0 SC engine have the oil squirters to keep it cool and lubed? The 4.2 SC has them as I recall.

 

nothing wrong with different views. That's what makes the world go 'round, but the subsequent comments have me baffled, to put it diplomatically..

The number of people on this forum who know every nut and bolt on numerous Jaguars is staggering, often getting paid for their knowledge on many levels, not just "...even as a Jag engine mechanic...".

Even being newcomer to the forum , I know the insides of every engine made by Jaguar from WW II to the mid 1980's. Not claiming to be any kind of expert, but long ago I made my living for many years by knowing the inside of Jaguars, as well as Aston';s, Triumphs, MG's, Lotus, Shelby's, and and Cobra's. . And my experiences pales in comparison to many contributors here.

I'm all for your inclination to get more power out of your car, and keep it "all Jaguar". How you go about that will be interesting for all of us to follow. Please keep us posted of your decisions and work.

Here is one of my e types in the late 1970's right after I'd changed a head gasket and did a valve job. The following day I drove it essentially non-stop from Oklahoma to Santa Monica California, averaging 90+ mph the whole way.




Z

 

[Did the 4.0 SC engine have the oil squirters to keep it cool and lubed? The 4.2 SC has them as I recall.}

I have in my possession 4 different versions of AJ-V8 oil pumps.
1. 4.0L oil pump.
2. 4.2L NA pump 1999 to 2004
3. 4.2L SC oil pump 2002 to 2004/5
4. 4.2L oil pump 2005/6 and newer.

The 2008 4.2 SC engine I purchased does not have oil squirters. All of my 2003 STR engines have the squirters.
I believe there is a forum conversation about oil squirters, but can't remember the details.
I thought that when VVT was added to the SC engine, they deleted the squirters.
All of the NA blocks I have have the flats without holes drilled, Squirters can be added, if you can find them.
(I have 2 spare SC engines, and 4 other blocks/bad engines I have accumulated over the years. )

 

Definitely agree here. I would love for you (@Higgins) to go through with modifying your 4.0 S/C engine, and do keep us posted. But as zray said, there are many master Jag mechanics here, and many engineers who are not only experts in these cars but also in a plethora of others (I don't claim to be one, by any means). I found my current independent mechanic on this forum for the rare thing I don't have time to do. Just want to give due credit to the forum--the lack of hopeful suggestions you're getting here is not due to a lack of knowledge but rather an abundance of it. Many brilliant souls have tried to tread these same waters.

That said, as in all good research, I am certainly rooting for you find success in this. Any new discoveries would certainly be beneficial to many of us. Keep us in the loop!

 

Mr. Higgins,
I've read all of your input on this Forum and you're right! We probably don't have any Jaguar Engineers on the Forum, but we do have several Engine Mechanics, Brutal (Bill) being one of them....So what is said here is not all BS! Now, as far as the 4.0 Engine...There were lots of mistakes made when this Engine was developed and it took until the 2000 Model before that changed. By then, those Engineers had started listening to the Mechanics an replaced or changed all those mistakes......Then in 2000 the 4.0 Liter (which is a "Square" Engine) became what it was supposed to be all along, a "Super smooth Little Motor"....then all of a sudden those Jaguar Engineers discovered the "Super-Charger" which created the XKR and at that point the XKR was "The Car"! I couldn't wait to get one and when I did, the first thing I did was get "The Big and Little Pulley Kit for the S/C and back then you could send the ECU up to NY and Phil would "Program" it for you, which today can't be done...After the change over the "Cute little Motor" became a really decent .Engine!...then after "Cat-Back surgery" and "Methanol/Water" injecting, it would run with the "Big Boys" and it was FUN! So, if you want to rebuild your 4.0, I would say "OK" by me.....but as I found out later, the same as most of the other Guys, the 4.2 is just overall a better, stronger and more efficient Motor overall.....
I would say though,, "If you want to keep your pre-2003 XK and the Engine gives-out.....Have it rebuilt and be Happy with it! After all, it is a beautiful Automobile! So, now, Mr. Higgins. it's up to you!

Billy Clyde in Houston

 

4.0 SC does not have oil squirters.

 

A comprehensive Jaguar account of the modifications and upgrades done to produce the 4.2 liter version from the 4.0 is all detailed in this attachment. Although overall it's covering the S Type model, the section on the 4.2 V8 is applicable to the XK range. It starts at page 42, after the 3.0 V6 section. It answers some of the questions and settles some of the uncertainties!

http://www.jagrepair.com/images/Elec...E%20Update.pdf