Hi,
I have got a catback Milltek exhaust on my x100 Xkr 2000. I gives a nice v8 sound and maybe a few extra horsepower as well. But as I understand there are more to sound and power to be found in the cats and exhaust headers. In some forum threads people suggest to switch to X308 headers since they should be better flowing the gases. Any thoughts on this?

Regards,
Higgins

 

No ideas here?

 

If you do a parts search using SNG Barratts catalogs you will find they are the same part number and are interchangeable between the XK8 and the XJ8. Since they are the same part number I doubt there is any difference in performance.

 

Mr. Higgins,

My 2005 XKR Coupe has XJR Manifolds (X308). Reason is, when my Right Cat burned-out and I found the cost of replacement @ some where around $1,850.00......I knew there had to be a better way!

My Jag Place here in Houston had a XJR from a previous Flood and had taken the Engine out, as one of the Rods had bent. I noticed that the exit area on both it's Manifolds had a Ball Joint that 45'ved out the back, instead of dropping straight down in a 90 with a gasket Joint like the XKR....That's a big turn and because of it, there has to be another 90 at the other end. Those (2) 90's tend to interrupt the flow of the exiting gases. So, I took the Manifolds off my XKR, including both Jag Cats and replaced the Manifolds with the XJR's and made up a down pipe that drops down at a 45 degree angle to (Two) Magnaflow 200 Cell Cats and then made up another pipe that makes a 45 into a Magnaflow Double Muffler......The Double Muffler, which acts as an X-Pipe, replaces the Jaguar silencer and then all this goes into what's left of my Quicksilver system. The total cost of this replacement was less than half the cost of (1) Jaguar Cat......

So, the answer to your question about the X308 Manifold is: YES they will fit the XKR Engine but you have to modify the down-pipes because of the 45 degree angle of the exit. Currently, I'm having another Set of XJR Manifolds Ported to match the diameter of "Sweet Sugar's" Ported Heads and smoothing down the interior for better flow. When they complete that, they will go over to "Poly Dyn" to be Ceramic Coated inside and out, with hopes of even more flow due to the smooth "Ceramic Coating".

One last thing that you have to do is to extend the length of the EGR pipe, so it will reach the connection at the bottom of the throttle-body.......It's made of Brass and has to be braised.

The sound of the System is abit louder now than with the original Manifolds and it sounds a little more throaty than with the XKR system.

If you want to try this and need anything, Just let me know!

Billy Clyde in Houston

 

The information for the 2005 XKR versus XJR is correct. But for the 2000 XKR versus XJR which has the 4.0 liter engine the manifolds are the same and are interchangeable.

 

Avern1,

Sorry, I don't remember exactly how the Exhaust Manifold system was routed on my 1998 XK or the 2000 XKR but I sure did think they were the same as my 2003 and 2005 XKR's. I didn't have the Cat problem with either of those older cars and it has been a long time since I last owned a 4.0 Liter......You may well be right on the 4.0 Liter! If so, mark one up for you!

Sorry, but I guess I'm gonna have to look for myself!.........

Billy Clyde

 

Thanks for all the info Billy!

Avern, do you meen that the info Billy provides about Xkr manifolds going in a 90 degree turn is only true for 4.2 liter engines? And that Xkr 4.0 liter engine manifolds use the same 45 degree turn, just like manifolds from X308?

 

The parts catalogs for the XK8 and XJ8 list the same part number meaning they are the same. The parts catalogs for the 4.2 liter engine each have a different part number for the exhaust manifolds. There has to be some difference since they are not interchangeable.
I would recommend visiting a local wrecking yard and take a look at the manifolds. I am confident you will find them to be identical.

 

Thanks for the advice. If my car has got the identical exhaust manifolds as Billy refer to as X308 manifolds with 45 degree outlet angle, I will probably stick with them and concentrate on changing the cats to 200 cells. With matching downpipes to fit my Milltek cat back exhaust

 

Mr. Higgins,

As I said I would, I looked and here's the real deal! All 4.0 Liter Engines have the same Manifolds and big Can looking Cat Converters.....The system comes out of both sides of the Engine from a Manifold that makes a 45 and Bolts-up to the big Can looking Cat. The Cat has a neck that 45's off the top and matches up with the Manifold's 45 where there is a "gasket" between the two where they bolt together. This is also true for all 4.0 & 4.2 XK8 & XKR's until the 2007 Model came out.

When the XJR changed to the 4.2 Engine, Jaguar changed that Manifold to the new Ball Joint that also 45's out the back but this time it hooks up to a Pipe that continues down the side to a Regular looking Cat and on down to the XJ's Exhaust system.

So, if you want to use the new Manifold with the Ball Joint connection on your 4.0 Engine in a similar fashion to the XJR....You would have to make sure the bolt pattern on the 4.2 Manifold is the same as the 4.0. From that point on, if they will work it's a matter for having a good Muffler Man or and Exhaust system builder and probably about $1,500.00 Bucks. You can buy those 4.2 Ball Joint Manifolds from eBay all day for about $60.00 at your door. The other way is to find a wrecked 4.2 Liter XJR and buy the parts that you need from it.....probably the best way! Your Luck as Jaguar has done the work for you with the XJR....Not so with the XKR.

Sorry for all the confusion about the early XJ's as I have never had much to do with them. My first Jaguar was a 1998 XK8 Coupe and I think I rode in an XJ one day going to Lunch with some Guys.....When I put the Barlo System on my 2000 XKR, we just hooked-up to the bottom of the big Can Cat like you did with the Milltek system.

Good Luck to you if you continue this project! It works well and sounds really good....not to loud but you know it's there!

But in the end, Mr.Higgins, Like my old Dad used to say, Jaguar has spent Millions of dollars designing this Car so it would be reliable and still perform nicely. So why change things? Think about it!

Billy Clyde

 

Fantastic research, well done Billy! Appreciate it alot. Lets see what solution I will go for in the end.

Regards,
Higgins

 

ceramic coating.....Look into Swaintech. They have lots of coating including a high flow coating which ive used on intake manifolds and intake ports on heads