I picked up a 99 XJR for about 1200 bucks about a month ago. I have been working on getting it back on the road since then. I have a lot of experience working on cars (built a race car with a full standalone ECU, wired the entire car, built the engine etc.) and so of course I can't leave anything alone. The plan is to make this Jag my daily, but one with a little extra sauce.

Like any good boy, I have been searching the ever living s&^% out of this forum and have learned a whole lot which is great! Unfortunately, some of the information I have found is now out of date (items no longer available). I would like to see if some others here can share some information regarding what's available in 2024 for bolt-ons etc.

So far I plan to do the following:

1. Timing chain guides. My motor is an AJ26 (unfortunately) and so it's got the bad guides. This is already in process. Supercharger is out etc. and I will be pulling the timing cover tonight. I am going to take this opportunity to go through the entire car (send out the injectors, replace all of the gaskets, water pump, vacuum lines etc.
2. Upgrade the SC to a Gen V. I ordered one on eBay for 300 bucks. I will port the TB elbow, charge coolers, intake plates, and anything else I can get to as much as possible. All you need is the 4.2 inlet gasket and a dremel. Done!
3. Intercooler pump. I'm going to use the one from the Mercedes AMGs.
4. Upgraded pulley's for even more boost. Probably go right for the 3lb.
5. Larger throttle body.
6. Superior intake tract.

Numbers 5 and 6 are where things get challenging:

5) Apparently Maxbore was the place to go but they do not do the TBs anymore. Some are reporting going from as small as 75mm to 82mm. I don't know if the TBs are different on the AJ26 but mine is already larger than 75, much closer to 80mm as best as I can measure. My calculations show I can maybe gain 10-12% of area max boring the throttle before I start to run out of wall thickness. I believe this still may be worth doing but it wouldn't be a huge gain. Would this be worth it?

6) The intake is a massive restriction on this motor. It's obvious just looking at it. The motor makes 370hp and has a smaller intake than what I had on a 190hp E34. I am not interested in a Mina Gallery intake. In my opinion it is still much to small. Ideally a 3.5" at least or even a 4" would be better given the overall length. I can fabricate this out of off the shelf parts as others have done here but the MAF on this car is absolutely tiny. Not only that, but the sensor itself takes up even more space on the other AJ26 units like I have.
This thread has some nice photos demonstrating this. Ideally I could switch to a Pro-M unit as some others have done here in the past, but.. *drumroll* it looks like they have put us out the pasture . See post number 4 of this thread here.

Does anyone know of any other options for a larger MAF similar to the Pro-M unit that wouldn't require any tuning? In the very likely event that there is not, does anyone know how to at least make an AJ27 MAF work on an AJ26? It seems there is a way based on the discussion in the first of the two links posted above, but no details were shared.

If there is anything else I'm missing that can give me some extra whp please toss it out!

 

if you already are doing tensioners, I would recommend doing headgaskets as well. The 99 and earlier composite gaskets aren't reliable when you start pushing a bit harder. MLS gaskets from a 4.2 are the way to go.

I've done just about everything you're thinking of here (3.5 intake, gen V eaton, larger crank pulley and smaller blower pulley, amg IC pump, AJ27 MAF, etc.) and my car runs great. Going beyond this point makes less and less sense to me as there isn't much support for this platform anymore.

 

The AJ26S is a good engine. If you’re in it for a little extra power, definitely do as suggested and do the MLS head gaskets. However, I’d get the heads decked, complete valve job and have the machine shop do the valve adjustment. I would also try and get new valve springs if you have a bunch of miles on it like 150k+.

I also got a harmonic balancer from an 09’ XFR because the drive pulley for the blower is larger diameter than the stock XJR. I would advise against getting the 3lb blower pulley unless you have a machine shop. The blower snout needs to be precisely machined for that small pulley. I’d get the 1.5lb upper pulley for the blower instead.

 

This isn't a bad idea. It wouldn't be too much harder to go ahead and do the head gaskets. I'll have to check and see if the gaskets and other items I would need are available. I'm assuming all of the hardware needs to be replaced when doing this? Ugh this is a slippery slope .

Very cool. From what I can find it appears there are only 6 ribs but other than that it's a direct swap? What belt do you use? Any issues running this with a Gen 5 blower?

I think I am going to try and bore the throttle. I have access to a machine shop and solidworks, I am more concerned with taking the unit apart .

 

That's real because limited parts option it's not Honda k series or Toyota 2jz there's barely any performance parts and it cost $$$ I didn't see any other company make cold air intake except mina gallery

 

MWC, I can provide you with belt and pulley information but it might be a few days. It’s kinda a lot to get all the parts up and posting my explanation. I’ll try and work on it.

 

Thank you! That would be awesome and very much appreciated.


So I'm definitely going to go ahead and do the head gaskets. Is the standard gasket from a 4.2 SC ok? What are the recommended head bolts? Any reason to go with something from ARP or are the standard 4.2 bolts ok? I love this design where the flanges for the downpipes are so close to the heads. Not having to wrestle with the header bolts in the engine bay is great.

On a separate note I managed to snag a running and driving R1 package car for $1000 this past Tuesday. I'm going to steal the Milans and brembos for this car and a whole bunch of other parts I need here and there. Very stoked on the wheels and brakes.

 

Standard gasket for the 4.2 SC is fine. I used the Payen ones, which i believe are oem. AJ88988 and AJ88987

ARP does not make a bolt or stud for this car, which is annoying as I would have liked to use them as well. I ended up using the felpro bolts, which are supposedly not quite as strong as the original ones, but they are holding fine on my car at 15psi.

As for pullies. I used a pulley from a 2007 XJR and added a 6 rib water pump pulley as well from the 4.2 to assist in belt tracking (not that it was an issue). I used the CRP Automotive ContiTech PK060935 belt.

Good deal on the R1. I might be interested in some parts if they are in good shape (primarily drivers door wood trim).

 

Raceware can make a head stud kit; just click on the name. You do have to email or call them and they will fit in the Jag studs during their production runs.

I got a ProM MAF with a Jag 4.0L tune about a month ago that I'll be fitting in July along with the Raceware studs and couple of other things.

 

You going to pull the head, or just swap one stud at a time?

 

I'm going to have to do the later; one stud at a time. I wanted to pull the heads but we've had to spend a (adjective deleted)-load of money this spring. New AC unit, dog with congestive heart failure; took a bite out of my hot rodding budget.

BTW, I've been thinking about the torque for the studs. The instructions from Raceware just address the studs and make it sound easy when you get the cams out of the way. Since the studs aren't going to stretch like the bolts, I'm trying to come up with a number that would be almost 35NM plus 90 degrees. Any thoughts? There's probably a thread somewhere in the forums, but I haven't done a search, yet. And, I'm hoping to do this without pulling the timing cover.

 

How is it refitting the heads with studs in place? Are there any issues with room? Seems like there may be issues with clearance. I'm honestly not entirely sure that they're necessary with these relatively mild mods.


Did you get this MAF from Pro-M or second hand?

 

You can always install the studs after the head is placed on the dowels.

 

I made an comment on another recent post about the X308 caliper options to a newer fellow member. I think this statement should apply for those young folks just recently acquired a X308 for cheap and thinking just work on their project DIY.

while X308 was my dream car and got mine at a relatively younger age of myself also . please don't take my word in a way I am discouraging you or even making fun of you here but just some sincerely advice

welcome to our community and allow me to say a few words...our Jaguar X308 is not BMW, mustangs nor Corvettes,not any JDM. we will not and never have many aftermarket supports and options for parts, upgrades. sometimes we can no longer get the OEM parts brand new anymore. that is something each of us needs to take into consideration for owning a X308. you will be a lonely warrior by yourself (outside of this group) and we need to accept the terms and conditions as is.

I am certain you are pretty handy working on cars even at your young age but X308 is both old and too complicated to fix sometimes without prior experience and knowledge and specifically chasing the power gain game on this platform is less realistic and more changeling. it is old and it has more then enough decent power that car chassis can handle. you will NOT not get cheap power gain and that is not the whole point of owning a jaguar.

cheap and fast and aftermarket upgrades ability and availability WILL Never be an easy game here. I hope you just need to ask yourself clearly is that what you really want.

ok..otherwise again... welcome

 

on the other hand, there is this solution:

https://boostdistrict.com/products/l...ystem-w-6l80-e

 

Thank you, I certainly hear what you're saying. So far the biggest challenge has been locating parts for all of this work. I have so far managed to find it all, but not in one place (PIA). So far this site has been a godsend.

To be fair I am not that young at 33 , and I personally do not find this car to be very complicated. It is a very basic port injected V8 with no VVT etc. I have so far found this motor to be a superior, more logical design than the BMW M60/2 counterpart I am also very familiar with. Really making a little more power on this thing is very simple: spin the SC faster and find clever ways to make it breathe better within the limits of the stock engine management.

That's cheating!




... (you're not wrong )

 

Adding to Quad's comment, yes, there's a room issue as the heads will have the exhaust manifolds fitted. I've jacked up the engine far enough to replace the motor mounts, but I think it would be too unstable to mount the heads. To jack the motor I removed the bottom motor mount and trans mount bolts and put a nice piece of 2x6 between the oil pan and jack. If you did this to fit the heads, the engine would probably roll to the side that you're doing first. So, fit the heads then twist in the studs. The head bolts are stretch bolts and they will stretch when under WOT, even with a completely stock engine.

Brand new from Pro-M. I ordered it on the website and they have a selection for Jaguar under "Non-Ford vehicles," so I just put in the comments that it's a 4.0L SC engine with stock injectors. You will also need their wiring harness and an IAT sensor. A2b provided the part number for that. I got the 80mm plastic one for a couple of reasons. The first being that the TB is 75mm and as you found out, Max quit boring. The other reason was so that it will fit in the area of the original box. It's much larger than I anticipated, so I'll have to do some fabrication for hood clearance. For now I'm sticking with the 3-inch Mina Gallery tube; might get a carbon fiber tube once I get it fitted, but if there's a chance of getting the TB bored, then I'll go bigger and definitely go with the carbon fiber tube. So, let us know if you're going to be able to bore yours, please.

BTW, I was 33 in 1987.

 

This appears to be a great deal of work. Sometimes it is just a joy to
"fiddle" with our cars. The engineers put much thought into the layout
and integration of these lovely ladies. It is good to see that momentum
carries on with changes that enhance everyday performance.

 

@MWC:
Maybe you can make use of my thread as well:
https://www.jaguarforums.com/forum/x...e-swap-266724/

It's the timing chain swap (incl guides and tensioners) on my 1999 X308, BUT not SC and no VVT.

You posted that you will swap the guides - you did not mention the tensioners, which will be just as buggered.
And why not swap the chain and "sprockets" (lacking a better word) as well?
Note that I have chosen a budget chain kit (with tensioners and guide), and meanwhile I saw a post, where some are skeptical regarding the quality of budget chain kits. I do not know, what to make of that, but I just wanted to give you the full picture.

 

OP, I like where your head is at. You have been given excellent info. My car is relatively stock(see signature), so I can't be of much help. But, I don't think I saw this mentioned. Blower cars benefit decently from a free flowing exhaust. Shed some weight if you can. Though that will be hard. Other than exhaust work and spare tire. An LSD should be worthy on these cars. Qauife sells them.