I'm sitting here in lockdown thinking about the things that I would like to upgrade on the 2.4 MK2 that i'm building and have produced a list of things to look at, does anyone have any experience of the following:

Dual Circuit Brakes

I've looked this up a bit in the past and found that people recommend the 420 braking system but when you look at it this is actually not entirely dual circuit as the master cylinder to servo connection is still a single circuit with a single point of failure.

Has anyone fitted anything else? I wondered if I could use a pedal box from an X300? https://www.ebay.co.uk/itm/Jaguar-X3...4383.l4275.c10

The angle of the base plate looks similar to the bulkhead mounting on a MK2? Surely with a little fabrication it might be possible?

Power Steering

Here is one that is the subject of much debate, i'm not keen on the electric column as the main critisism of my 3.8 MK2 is that the steering takes so many turns to go from lock to lock and putting an electric column in won't help that unless I can find a higher ratio steering box which are very rare and expensive.

The factory power steering boxes seem to be either expensive, prone to failure, hard to rebuild or a mixture of all three.

I had an S-Type with an XJ6 rack in it which was fine (although I know a lot of people disagree) but also noticed some conversion use an XJ40 rack and did wonder about whether anything else (like an X-Type rack) might be a better fit? Does anyone sell just the mounting brackets rather than a full kit?

I would look to fit an electric power steering pump rather than mechanical, any recommendations (UK), the Vauxhall Astras seem plentiful, any experience of making these work?

Brake Callipers

I've got a set of rear 420 callipers that need rebuilding, these seem to have the more conventional type of pistons and look like an easy fit to a MK2 other than some slightly longer bolts and a spacer to centralise them, has anyone done this and if so is there anything else to consider?

The front brakes are bit more of a challenge, are the S-Type front callipers of a more conventional design (seal in calliper and piston runs on seal rather than the MK2 design)? I seem to recall that they might be? Is it possible to fit anything else that doesn't need a lot of work? I have heard that Volvo 240 callipers can be made fit if you get the right ones but the disc needs turning down. Any idea which year Volvo the callipers need to come from?

Are there any others that might fit? XJ6 etc?

 

the S type's "power assist" is a Ford tractor system from the late 1950's which as you know, is connected to the generator. You can get the filters for these systems at Tractor Supply houses. Totally useless if you ask me. In fact the entire front steering system of the S type and MK-2 are primitive, stone-age systems. I understand that rack & pinion conversions improve the steering and at the same time degrade it.
So I have opted to leave my S type as it was designed, it is too complicated to improve and I am no scientist.

 

I have to say having owned both a car with an XJ6 rack conversion and now one with a standard low ratio manual steering box the XJ6 rack conversion is far superior and made the car much nicer to drive.

I personally didn't really notice any of the downsides that people talk about (ackerman angle etc.).

The XJ6 racks are getting more rare and expensive hence wondering if there was a more modern alternative and also interested in what the difference between the XJ6 and XJ40 conversions is.

 

I believe the XJ-6 rack is a GM rack, just like the Saginaw power steering pump. the Delco ignition module, the Delco Air Pump and related parts, the Power window motors, and many other GM components used in the XJ-6. The electric door mirrors came from American Motors. The Delanaire a/c system from a company in Texas.

So a GM rack cannot be that difficult to find. Buick, Pontiac, Oldsmobile from the late 1970s all the way to 1988 are a great source of parts for XJ-6. All GM racks need are 4 seals to rebuild them if they leak.

as for the XJ-40 rack, don't know.

Who would know? John at John's Cars in Dallas. He deals with 700R transmission conversions for XJ-6 and MK-2, and sells a wonderful kit of poly bushings for the XJ-6 rack to eliminate the side-to-side movement of the rack, typical problem in the XJ-6.

 

The Marles Variomatic Bendix Power Assisted Steering system is considered a vast improvement by most. (Jaguar call it Varamatic.) I've driven a car thus fitted & it's a big improvement over my "Second Type" Burman box with lowered ratio & torsion bar operated quill valve fitted to my S type. Torsion bar Type 2 feels a lot better than the Type 1

There were 3 different boxes fitted to the S Type. Burman types 1 & 2 & the Varamatic.




Courtesy James Taylor.

 

I have gone thru a series of brake upgrades but all are still using the stock single master and while a dual would be nice it was just more work than I wanted to tackle and right now I am ok leaving it with the single. What I would say is that I first started out with the Wilwood kit and it was an improvement but I found out later it was not adequate for my needs. The reason is that it still uses a non vented rotor. I did a very aggressive 3 hour drive with a spirited group of performance

drivers on the streets going through non-stop mountain twisty roads and the Wiwood could not handle it. The brakes got so hot that the brakes were gone in about 2 hours with the pedal almost going to the floor so I had to back off and drive like an old lady and after lunch the pressure was back but it pulled to one side. I found out that going into that drive I had 50% pads and afterwards the pads were gone and the rotors wasted. I now have what I think is the best brake upgrade for the fronts which is the New Six Pot Front Brakes for E-Type - Fosseway PerformanceFosseway Performance
These work great and feel like a modern day high quality brake setup. Some may say 6 pot is overkill but I do not think so as the MK and my 3.8S really need way better brakes. The Wilwood is just barely ok to me and any other use of some other Jag brakes would not be good enough to me. I did do the upgrade of the larger inboard E brakes in my 3.8s but like any car the most important is the front so while that was good the front is really what matters when typically 80% of your brakes are the fronts. I did need to add a proportioning valve to get the balance ideal. I think doing the 6 pott Fosseway brakes would be way better to do than attempting all of the likely complex and fab issues of trying to go with a dual master.

I also used the XJ steering rack upgrade and found no issues other than in my car I needed to add a finned cylindrical cooler to keep the power steering fluid in good temps and I used Red Line Power steering fuild.

 

With the rack conversions I'm sensitive to the Ackerman angles being way out & causing slip/scrub of the front tyres. Depends on whether this bothers people or not.

 

You can adjust the suspension settings with shims, tie rod adjustments, etc. so that is not an issue. I purposely set the suspension with just a very mild negative camber for better handling and am getting full tire miles on the tires with just a very slightly more worn inner section of the tires. Greatly improves performance with no extra costs in tires if the camber is not too negative. Adding power steering makes the car a pleasure to drive and you can set the suspension to remain more stock in feel or more for ones desire performance, that is a preference.

 

Yes ~ but no rack system retrofit maintains the Ackerman angles & you can't correct it. You would require to redesign the entire front end. Connecting an end steer or centre steer rack direct to the hubs makes it impossible. Racks push & pull equally on both sides. You need a system of levers to achieve correct Ackerman angles & differential inner wheel attitude to outer wheel attitude in a corner. i.e. In simple terms one wheel needs to turn more sharply than the other.

Ackerman steering geometry is used to change the dynamic toe setting, by increasing front wheel toe-out progressively as the car is turned into a corner & thus obviate scrub. The outer wheel has to travel further than the inner wheel when turning a corner. Both wheels need to turn around a common centre which is way outside the boundaries of the car in the direction that you are turning.

 

On my Mark 2, for the past five years, I have used a rack conversion supplied by XKS unlimited and the car is very pleasant to drive. While acknowledging the issue of bad geometry, its effects I do not experience in the normal sort of driving I do. However the price you pay is in tyre wear and mine were unevenly worn after maybe 10,000 miles. So I regard this simply as the price to pay for the benefits the rack provides.

 

Yes ~ some are less sensitive to it than others & happy to accept the tyre slip/scrub & shorter life. With the drivers window or NDV open I can't stand the noise & fact that the one wheel is fighting the other & scrubbing the tires when cornering. It's personal preference & what you can live with. I want both wheels turning around a common centre.

Also in my case I was trying to build a concours car & originality was important to me.

 

Glyn, You are a concourse person and not into modifications which I understand and respect but many others want a more modern performance driving Jaguar. The original poster of this is not a purist but wanted opinions about modifications. I have modified my 3.8s as you know a lot and in the front suspension it has a custom lower A-arms with adjustable coil overs, the rack and pinion kit, and custom offset wheels. I was able to get the car suspension tuned and the numbers are good as the car handles incredibly better than stock and the amount of miles I have obtained from my tires is at the normal max miles the manufacturer states and there is not weird or noticeable noise whatsoever. The rack upgrade is a definite upgrade as it is so easy to steer, park, and I am running 17" x 8.5" wheels with 245 wide tires on all four corners and it is so easy to steer and drive for long drives. I have put now over 120,000 miles on my car in the last 3 years since it was completed so I have real world experience of going through sets of tires in daily driving.

The brakes are another area that the Jaguars lack and after going thru the Wilwoods which were marginal but ok if you never drive a lot nor drive very hard; the Fosseway 6 piston brake kit made for our Jaguars is a great upgrade as you get impressive stopping power without changing the master, etc. That is well worth the cost and makes the car so much safer in general driving and finally up to par with today;s performance sedans. I highly recommend the Fosseway brake upgrade over the Wilwoods and trying to use 420 brakes or some other cheap swap. Again, I drive my car, don't trailer it, and push in several times a week thru canyon curves typically double the posted speed and drive often up to 85 mph regularly with an occasional burst when the coast is clear to 110 mph. The car is smooth, no tire noises, handles great, and just a blast to drive...

 

Thanks guys for all the replys, I can see both sides of the original and modified arguement and while the current 3.8MK2 I have is totally standard (apart from radial tyes) I would like to carry out some modifications to make the next one a bit more usable.

The standard manual steering is just too vauge for my liking and I would like to add dual circuit brakes for improved safety.

I never found any problems with the XJ6 rack but a lot of people talk about it so either I was lucky or its been blown vastly out of proportion.

I have found the standard brakes on the MK2 and the S-Type I had before it to be fine (although I did have a total brake failure on the S-Type at 50MPH approaching a 90 degree bend, hence the leaning towards dual circuit on the brakes). The main reason for looking to change is that the cost of the MK2 wheel cylinders is significant and having the seal run up and down the calliper body is unusual so not many people can rebuild them (and hence they are relativly expensive). I may just fit the 420 rear brakes and fit standard MK2 fronts (it is only a 2.4), just need to check on the brake balance.

I appreciate you can go even further with the mods if you drive ther car hard, at the moment i'm more into making minor modifications to improve the driving experince rather than radical alterations. I would still love an XJR transplant in one though....

 

did you install the Saginaw power steering pump with the rack & pinion? My XJ-6 is satisfactory with the GM factory system, and it is a lot heavier up front than my S type.

Otherwise Homer, install the factory power assist system to your S type or MK-2, it is not state-of-the-arts, but it works. You will need the generator with the adapter.

if you do not want a generator, RetroAir sells a 70 amp alternator with adaptor for Mk-2 factory power steering which should fit the S type.

 

I respect that. As long as one appreciates that you can't get the Ackerman angles correct & will suffer scrub with a standard retrofit rack. One could take a centre steer rack via a series of levers & achieve correct Ackerman angles which would be optimum for handling but effectively a full redesign. This is what the racing fraternity does for best roadholding performance & thus highest speed cornering with a rack & pinion system. Then they achieve the full benefit of a rack & correct Ackerman angles.

I'm not so much a concours person, other than on my S Type. I am a person that if I do a mod I want to do it properly. e.g. I like the idea of dual circuit brakes. But not the half hearted effort that was done on the 420.

 

Hi Homer, I'm also looking at this, and would like to have an idea in my mind of how to achieve it before I start work on the front subframe refurbishment. there's plenty online about the XJ6 rack, but it is too long and introduces well documented issues which I won't repeat here. But I've also heard that people have used the X-Type rack, which is apparently much shorter, so in theory, should be a closer match to the original . The X-Type racks are certainly more plentiful and cheaper than the dwindling XJ6's, so is there a reason for their lack of popularity I wonder. I've not seen a proper write up of anyone completing this, so information may be hard to come by. I need to investigate further I think.....

 

I've not come across the X-Type rack being used although it may be possible, the thing to consider is whether that rack is the correct length or whether it is too short (i.e. the opposite problem to what you get with the XJ6 rack conversion) and if so what effect that would have on the steering, i.e. if the XJ6 rack being too long caused toe in bump steer would an X-Type rack cause toe out bump steer and would that then be better or worse? Its something you need to really look into before going down that route.

At least with the XJ6 rack its a tried and tested solution and I do have to say that although a lot of people are quick to point out the technical short comings of the system a lot of those commenting have never actually driven a car that has the system fitted and are just repeating what is said in the many different forum threads panning the system.

I've had one fitted with this system and I was happy with it, what would be interesting is to see if anyone has fitted one and then removed it and gone back to the standard system? It would also be interesting to see what the change in toe is on a car under suspension travel with the XJ6 rack compared to the standard system.

 

I investigated the X Type rack on Dave's (Daimler Guy's) recommendation - as I recall the length between ball centers was not significantly different than the XJ6. While the front track on the X Type is narrower the rack is situated very high relative to the control arms, so the rack is longer than one might expect. The Mark 2 forces the rack to be positioned at or just below the lower control arm pivots which aggravates the length problem. If availability is becoming a problem you might look into an X300 rack (I think the length is close to the XJ6, but I'm not certain). The most critical aspect to consider is rack position - it needs to be as high and far back as possible to minimize bump steer. The other issue is the stock steering arms which locate the steering link ball joint too high for proper geometry. I used an XJ6 rack and mounting kit from British Auto (now SNG) on a build years ago and was very pleased - it actually made the car pleasant to drive. I know XKs (now Moss?) offers a kit and I think there are a few others. Why don't we get folks who have installed one of these kits to jack up their front end and post a picture of the front tires - the one with little or no visible toe-in is probably the one to purchase. Ackermann angle gets a lot of discussion but unless you're auto crossing or parallel parking all the time it doesn't matter much. Hope this helps.

 

On my 3.8s I used a kit for the XJ6 rack from Jag Outlet but unfortunately he has retired but I believe his was similar to SNG's. I also upgraded the car with adjustable QA1 coil overs, and a custom lower control arm. FYI, I was able to adjust the suspension to get completely 0 camber flat tracking with no uneven tire wear; however I changed the suspension and now it has about one degree of negative camber and I still get full normal tire life with just a little more wear in the first 1-2 inches of the inside but the car handles much better with that setup. I found the use of longer travel QA1 coil overs worked great. I have over 130,000 miles on the car driving it on the street generally at spirited pace 70% of the time. The Jag both at 0 camber and -1 degree negative camber drove pleasantly and had no issues for general cruising around in the car. For me I drive through mountain passes and am used to doing so at fairly fast pace from being spoiled with my other sports cars so when I had 0 camber, the car was not handling the speeds I wanted to drive so I went to about 1 degree negative and that is very mild and it tracks so much better. She is not a sports car but holds her own on curves decently and that small amount of increased wear only on the inside does not affect being able to get full tire life as the rest of the tread will be at the wear mark when the inside has began to wear well past that. I do not have a spare tire due to other mods I did in the trunk but I am getting about 40,000 to 50,000 miles on Bridgestone run flat tires. My car has an aluminum block GM LS1 V8 and running the March Performance serpentine pully kit with the GM type 2 power steering pump with remote reservoir.

Homersimpson, I would recommend the 6 piston Foseway brake kit as I even had the Wilwood 4 piston kit and that was not enough for my driving and while you might not push your car as hard it is always good to have more brakes.