The rear axle of the MK1 and 2 is located on the extreme end of the rear spring leaf and is controlled by a torque arm on either side of the car running from a body mounting to a bracket on the axle. This then locates the axle in relation to the body and stops the spring winding up under acceleration torque somewhat like a trailing arm system. The torque arms are fitted with metal/rubber bushes and with age these deteriorate with a subsequent loss of “stiffness” in axle location and general handling suffers. Don't confuse the torque arm with the panhard rod, which runs laterally [across] the car from the right hand side to near the differential centre. It centres the rear axle and suspension.
On the red MK 1 I knew that these bushes were getting pretty bad. Every time I jacked it up I could see daylight through the rubber area of the bushes. I obtained a new set from Jag World [PH 3272 7287] and with some help from a friend who is a club member we removed the torque arms, pressed out the old bushes and inserted the new bushes. Note-I have seen an illustration of this operation in a UK magazine using a bench vice. They must be different over there because we used almost all of the force of an 8 tonne hydraulic press to get the old bushes out.
We also found that the right hand body mounting for the torque arm was cracked and required some serious oxy welding to repair before refitting the torque arm. It also helped that this fellow club member happens to have an electric/hydraulic two-post car hoist in his private shed. This made the job much easier.
There was no doubt that as I drove the red MK1 home that evening along a winding high-speed road that the handling had vastly improved
When it came to getting the white MK1 through a roadworthy one item that became obvious was that the rear shock absorber mount rubbers were completely perished and new rubbers would need to be fitted before it would pass. With that in mind I had the car on ramps at home and fitted the new rubbers by the time honoured system of lying on the shed floor and applying much grunting, effort and some amount of cursing.
Whist lying on the floor I recalled what Tony Herald had said about how he cleaned under his concourse car and thought why not start here? So I degreased and cleaned up the diff and the general areas under the spare wheel well and petrol tank area and subsequently applied some black paint etc. It sure looked better.
To my surprise when the car was on the hoist being checked for roadworthiness I noted that a patch of my new paint on the differential had been scraped back to bare metal. I then realised that the odd suspension noise that I had heard was not a noisy/squeaky shock absorber but was actually the differential occasionally rubbing on the body area immediately adjacent to the petrol tank. I did not point this out to the chap doing the roadworthy and he was more interested in tie rod ends etc. The torque arm bushes looked OK but more on that later
After getting the car registered I organised use of the previously mentioned club members hoist. Mark Miosge from North Qld. Jaguar Spares in Mackay [ph 07 4954 6003] had offered me a good deal on a pair of torque arms he had overhauled with new bushes for a customer who had never collected them. I had acquired them “just in case” I needed them. When we removed the old torque arms the bushes literally fell apart so what looked OK was in fact totally “shot”. The new torque arms were fitted with a subsequent improvement in handling and the elimination of the occasional squeak.
I have since noted that the red MK1 has a patch welded on the rear of the diff housing just where it would rub on the body. I presume this is an old battle scar from a previous occasion when the torque arm bushes flogged out
You don’t have to send a lot of money to the Poms to identify fairly closely when your MK1 / 2 was built. There is no doubt that the certificate they send you will give original details on the car which is nice to know but do you really need to know unless it is going to influence the concourse judges or increase the value of the car.
Upon being asked any question relating to age/build of one of these models I immediately reach for the Nigel Thorley “Original Jaguar MK1/MK11” book. This is an excellent publication and one of its endearing features is that it traces each model of car by dates of production changes to the assembly line.
Thus by knowing the chassis number and engine number it is possible to narrow down the production date to within a couple of months. E.g. the Mk 1 was in production from 1955 to 1959 and there were no less than 25 production changes, which average out to one every two months. These production changes are typically dated with a month and start off with “from chassis number so and so” or “from engine number so and so”. Simple arithmetic between the change dates and chassis/engine numbers will give an indication of the quantity being produced and from this you can make a reasonable estimate of when your car was built and more particularly what the production status of your car was all about.
Although this book is expensive at typically $59.95 it is the reference bible for anyone wanting to get their MK1/MK2 restoration correct and the colour photos of interior trim and changes in production are really good. The text is well written and is totally to the point. I.e. no padding-just information. I have read it several times and still emerge with some new snippet or fact that I have previously missed.
Another worthy publication is the “Practical Classics Mk 2 Jaguar restoration”. I wish I had read this years ago. It traces a project car that was professionally restored but at the same time as much as possible was retained from the original trim etc. For example it gives guidance on replacing the door trims by salvaging the original vinyl and attaching it to new backing boards. I have also used the same technique in MK 1s. There are literally dozens of photos of each step along the way and many hints and tricks are explained including how to find the hidden screws that retain trim and also woodwork restoration etc.
For the restorer of a MK2 [and a lot of the book also applies to a MK 1 particularly in the body and mechanicals] it is extremely useful and whilst not cheap at again $59.95 I believe the cost would be more than off set by savings made in the restoration process from the books recommendations on salvaging trim etc.
These books are available from any good motoring bookshop. The prices I have quoted are from a bookshop advertising on page 51 of Edition 101 the Australian Jaguar Magazine. There are also a number of other Jaguar models covered by the "Original " series of books as well as the "Practical Classics" publications. If they are anywhere near the standard of the MK2 publications they should be good investments. You could also enquire with our club librarian as to their availability on loan from the club library.
A number of club members have get involved in the ride height debate for a MK 1-2 Jaguar. It appears that 18 1/2 to 19 inches from the ground to the centre of the boot lock is about right.
However members of other registers have also done investigation into their cars and have found some to be well and truly in need of serious adjustments and repairs to the rear end. Malcolm Imrie who wrote an article for the Bits and Pieces section of February magazine on XJ6 rear springs provides a good example of “getting it right”.
The MK 1&2 Jaguar workshop manuals are a little skimpy about ride height for the rear end of these cars. Everybody knows that the correct height for a front end is about 3 finger widths between the top of the tyre and the bottom of the mudguard arch. In the workshop manual there is a specification for the amount of curve in the rear springs but that is about all.
It was not until I had the two MK 1s in the shed that I noticed there was a completely difference in the way the cars appeared to “sit”. The red car was definitely lower in the rear end. With a tape measure I checked the height from floor level to the centre of the boot look . To my surprise I found a difference of 2 ½ inches. The red one measured 16 inches and the white one 18 ½ inches. The difference really becomes apparent when you realise the red one is on standard 185x15 tyres and the white one is on 205x65x15 tyres that have about ½ inch less in tyre profile height.
I would appreciate any feedback from MK1 and 2 club members on the specific height measurement on their cars along with the types of tyres fitted. We have checked another club members MK2 and it appears 18 ½ to 19 inches to the bootlock centre is about right on 185x15 tyres.
I always thought the red car looked to be “dragging its bum”. Once I have established the correct height it is off to the spring works for resetting
When I acquired the MK 2 the tachometer [as well as the oil pressure gauge] was not working. It became fairly obvious that one of the problems was that the tachometer [tacho] generator had a broken electrical connecting lug. This tacho generator uses the same principle as a pushbike generator to create electrical voltage by rotating a permanent magnet inside a coil. This electrical voltage is then fed to the tachometer instrument, which in reality is a voltmeter. The principle is that the faster the tacho generator goes the more electrical voltage is produced which produces a correspondingly higher reading that we see as revolutions per minute [RPM]
This same tacho generator is also used in the MK9, S type, earlier E types and Daimler 250. Enquiries for a replacement tacho generator part no C14996 resulted in prices in excess of $300. Hmm –it was time to put the thinking cap on and see if repairs could be affected.
An inspection of the terminal cap of the tacho generator, which uses push on spade connectors revealed that the lug had been broken off flush with the surface of the plastic cap. By using my trusty dremel tool I was able to excavate around this broken lug to a depth of about 4 to 5 MM or 3/16 inch. I was then able to cut the male section of a spade terminal down to a suitable size and solder it to the old lug. The whole thing was then finished off by using a dam of masking tape to allow a suitable build up of epoxy resin over the excavated area and the base of the new lug. This all resulted in a now sound lug projecting from the terminal cap.
I had checked the wiring from the generator to the tacho instrument and all measured OK with about 2.5K or 2500 ohms resistance, which indicated a correct circuit impedance existed through the instrument. I replaced the tacho generator [with a new O ring fitted] hooked up the tacho instrument, started the car and achieved nothing. The b.......y instrument was U.S. ! [unserviceable]. I was also able to check that the generator was working as Ben Stafford had lent me an old battered tacho with a partly broken needle etc. but still serviceable as an indicator and I hooked it up and it worked.
Muttering and cursing I removed the tacho instrument [and a couple of squre inches of skin as well]. I cleaned off the workbench which is a miracle happening in it’s own right and laid out some clean cloth to allow me to dismantle the tacho. It does come apart very simply as the faceplate only needs to be twisted to align the spaces on the faceplate with the lugs on the case. The faceplate can then be lifted off. The tacho instrument itself is only secured in the case with two screws and the clock at the bottom can be left attached to the case.
Applying gentle pressure to the needle revealed that it would move but was rather bound up on the “jewels” or pivots. In my time as a radio technician and later on in aircraft engineering I had been exposed to and qualified to do instrument repairs. One facet of instruments that few people ever consider is that they do need lubrication. More particularly so as they get older and the original lubricants dry out. With an artists brush I applied some penetrating oil to each of the needle pivots and allowed it to take effect. After about an hour the needle was quite free and I applied some sewing machine oil to each pivot. The needle was now quite free and I reassembled the instrument. I made a temporary connection between the tacho generator and instrument, started the engine and wonders to behold it all worked.
Tearing off the usual square inch of skin in the process I refitted the tacho and reconnected the wiring. A quick check ensured that all was functioning and the beer fridge in the shed was raided to celebrate.
With two MK1 cars with sagging rear springs it was time to adopt production line methods. Mark Miosge from North Qld. Jag spares in Mackay [ph 4954 1420] mentioned that he had a good pair of springs and offered them at a reasonable price. In fact the freight was nearly as much as the springs. Inspecting them on arrival showed that they were good and did not require any re-setting. I visited Barry the friendly spring man at Pine Rivers Spring works [ph 3285 7383] and got him to fit the new spring eye bushes and rubber mounting blocks that I supplied.
A couple of hours under the car including welding up part of the left hand spring mounting box and the red MK 1 3.4 was back into action. It really does sit correctly and this is emphasised when the two red MK1s are sitting adjacent to each other. There is a really apparent rear end sag in the 3.8 car. The springs that came out of the 3.4 will be re-set and have new hardware fitted before going into the red Mk 1 3.8. I will then have a spare set of rear springs so if anyone is desperately in need of them contact me.
A club member advised me that he had a pre-cut carpet kit for his MK 2 that had not been put into his car. That got my attention as I have been to several upholsterers attempting to get a new carpet fitted to the Mk 1 hotrod. When it comes down to the crunch of getting a start date they all seem to find that they are too busy to do it. This has been going on for over 12 months and at the mention of the pre-cut kit I thought here is an opportunity that should not be let pass. I'll have a crack at doing it myself!
Club member obligingly produced the kit and I had obtained a couple of sheets of 1/8-inch [or approximately 3 mm] plywood. We laid the carpet components out on the plywood and traced around them with a pencil. Some careful work with a band saw and subsequent sanding and a couple of coats of clear lacquer have left us in possession of a set of templates for a MK1/2 carpet. I went off to Daly's and bought 5 metres of "Fina" red carpet, which is about $20 a metre. It has a particularly good backing, which cuts well and does not need edge binding.
That all took place a few months ago and I have been trying to find time to get at the carpet problem. The Christmas break afforded the opportunity to grab a few extra days leave and after the usual household chores I was able at last to attack the car on Boxing Day. What I did not realise is the amazing number of pieces of carpet need to carpet a MK1/2. The kit contains no less than 17 pieces and even then I cut an extra 4 pieces where I believed carpet should be placed on the centre cross member supporting the front seat and on the face of the pressing supporting the rear seat.
So far I have spent about 8 hours on the job. This included removing the front seat mounting brackets, stripping them clean and recovering them in vinyl. I expect another day of work to complete the job. I am not aiming at concourse but simply want the vehicle to be neat and tidy.
I also have to re-carpet the white MK 1 3.4 and as have I advanced somewhat along the carpet laying learning curve I think it will be a much shorter job. For club members who wish to do their own thing with a MK 1/2 carpet I will eventually be willing to lend the template set.
Very old windscreens are dangerous because they get badly worn with stone chips and general scratching. The windscreen in the red MK 1 looks OK but coming over the rise looking west just before sundown on the last lap home just like driving into a whiteout. I have had to put my head out the window to see forward.
I have also dreaded the possibility of getting a broken windscreen because I have only one spare. Repeated approaches to many sources for a new MK 1 windscreen have met with many rebuffs and continuous mix-ups as I try to explain that it is not a MK2 windscreen and YES THEY ARE DIFFERENT.
In addition some manufacturers have said that they will supply a MK 1 windscreen provided I give them a sample windscreen to make a pattern and order a minimum volume of 10 production screens. Heck there are only about 15 MK 1 cars in the club!
Finally I hit paydirt when I rang a local windscreen manufacturer by the name of “Moran Glass” at Tingalpa. [PH 3390 8855]. Peter Moran after the usual mix-up of MK1 versus MK 2 sorted things out and advised yes they could provide me with a MK 1 windscreen but would need a few days notice as they did not have any in stock. He had the dimensions off pat e.g. the MK 1 windscreen is deeper than the MK 2 and slightly narrower. He advised the price would be around $110 plus GST.
It was only after I put the phone down that I realised I knew the organisation I had been talking to. In fact my family and friends have done business in the past with Moran Glass. They replaced the windscreen in my son’s Toyota 4 wheel drive Ute, the Ford LTD and the Ford XF Ute we used to own and also a number of friends’ vehicles. We were all very happy with the service and the relatively low prices charged at the time. I also suspect that the new windscreen I fitted to the Series 3 some years ago came from there.
I recommend you check with this company if you need a windscreen. At least they are local for the Brisbane members.
The MK1 was inclined to pull itself into the middle of the road and make a Kamikaze attack on any oncoming traffic whenever I hit the brakes. It was definitely not the best way to drive and tended to worry oncoming drivers. After some serious analysis over a 6 pack I went after the possibility of failure of the left front calipers, however my mind said both left front calipers were rebuilt to new specification and a double failure/freeze up would be most unusual.
A simple check by cracking the brake bleed valves while my “dearly beloved” pressed the brake pedal showed little flow or pressure to the pair of LH front calipers. Further investigation revealed that the left front brake hose was blocked. When I put the brake system together a couple of years ago I had checked the hose was OK by passing a piece of wire through it. I had no knowledge of the history of the hose but it had looked and checked out OK. In fact due to age it was developing a severe case of a blocked artery over a short time period.
The offending hose was extremely difficult to remove especially at the body bracket end of the system. I resorted to the “hot spanner” i.e. oxygen/acetylene torch and after successfully setting the MK 1 on fire three times finally resorted to grinding through the retaining nut with an angle grinder. That got it off the car but my problems were not over. I then had to get a replacement hose.
Every retail source was checked and I kept getting the reply “not in stock”. Interestingly enough all the suppliers could quote me prices between $59.00 and $67.00. In desperation I contacted Graham Deahl who is the Victorian MK 1 register giru and explained my problem. He advised that they had similar problems with brake hoses and I had best contact a hose manufacturer.
I approached BPA and put the problem to them. The reply was laconic. Gary their technical fitter said
“ They had never been stumped by a brake hose” After examining the remains of the MK 1 hose said it was no problem to make me a new one with all new fittings. He also said that they had never had a hose returned after failure as their equipment was checked regularly by [transport?] authorities.
I asked what was the price?
He answered ” $60.00 - that is the standard price for a one-off hose”.
Me: Does that include GST?
Me; Are you approved to manufacture brake hoses?
He; “Yes” [and proceeded to show/tell me about the certification]
Me; How long for delivery? [Believing fittings would be a problem and may need to be ordered in]
He; “about 15 minutes or less if you are in a hurry”.
I said, “I am in a hurry but I’ll wait - make me two of them”
“OK” sez he
And that readers was what took place. About 10 minutes after the start of the conversation I had in my hand two brand new brake hoses to the exact and original specification for a MK1. I might add that I had spent almost two weeks trying to source a replacement brake hose.
I dropped in next day as I had a problem with the 5/8 inch 26 TPI nut at the body end. I had destroyed the original with the 4-inch grinder just to get the hose off the car without destroying the mounting bracket. Nobody could supply a nut however Gary sorted this out by re-cutting the inner hose retaining thread for a SAE national fine] NF] nut. I noticed about 150 new [after market] hoses he had just turned out for distribution into the retail market. He remarked that the hoses had been ordered the day before and he expected pickup at any time. In other words this company was seriously involved in after market supply.
Somehow I think we Jag owners believe that English magic is used to produce parts for our cars and it must be “original” to be any good. After market organisations like BPA turn out a product standard which is controlled by Australian government authorities and are more than willing and able to support our old car cause. The important thing for we restorers is that they can supply “one off” requests at short notice and within the normal retail price range.
I don’t apologise to our normal retail suppliers. Having copped the trauma of “unable to supply” or “not in stock” it is only fair that alternatives should be readily available to club members.
Brake Boosters Another issue came out of my visit to BPA. They are equipped to overhaul brake servo power boosters. This was qualified by remarks that parts are difficult to obtain on some types but the customer should liaise with them and they would make recommendations on the best course of action i.e. repair or replace with an Australian made product.
To get things into context you must remember that Sir William Lyons was attempting to break into the domestic sales area of the UK market when he first came up with the small 2.4 saloon which subsequently became known as the Mark 1.
At the time the Mark 7 was in production however it was viewed by the British as a large car. In fact the Mark 7 was aimed squarely at the export market as steel supplies in Britain were still rationed under a quota system. You could only get steel if you were in the export trade.
Sir William was no slouch in recognising that he needed a car which would be acceptable to the home market as being reasonably economical, fast and still be of a size easy to manoeuvre and park in the congested streets of that island continent. He also had to consider that in the UK domestic economy petrol was very expensive. Petrol rationing had only ceased in 1952 and nearly returned in 1956 during the Suez crisis.
It should be noted that in 1955 when Sir William introduced his MK 1 Australia was involved in a love affair with the FJ Holden which only ceased production in late 1956 It’s replacement which was the FE/FC series Holden was no faster. Sir William gave the world a twin overhead cam vehicle producing 112 Horsepower out of 2.4 litres or approximately 144 cubic inches, which did 100 miles per hour and easily did 100,000 miles without any overhaul. What General Motors sold to Australia was a vehicle called an FJ Holden with approximately the same capacity in a pre war pushrod GMH engine design that produced 60 HP, did 83 MPH and had a life of 50,000 miles between overhauls if you ignored the gudgeon rattle which started at 20,000 miles. In those terms alone the 2.4 Jaguar was no slouch. You could not compare the brakes and handling. The Jaguar was so far in front that it is like comparing a T model Ford to a post world war 2 car.
Anyone who has owned a 1950s British car will understand that the British paid slavish attention to fuel economy. The MK1 2.4 was no exception. It had a deplorable pair of Stromberg downdraft carburettors to miserly feed the fuel into the engine and a whimsical narrow tailpipe/exhaust system to get rid of the gasses. The early model also had very small valves. After all that, it is remarkable that the car did so well as to make 100 MPH. Some British reports claimed an economy of 26 MPG however in practice 22 to 23 MPG from a MK 2.4 is more realistic. By the way the MK1 2.4 was officially about 2MPH faster than the MK2.
Many 2.4 Jaguars imported into Australia are also saddled with automatic gearboxes, which further reduce performance. The old DG [Detroit Gear] series box, which is really, a Borg Warner 35 series in disguise does a good job but is very wasteful in power. They are also notorious for developing oil leaks.
What Are They Worth? Currently 2.4 litre sedans are very cheap and even an excellent example only brings a fraction of the value of a 3.4 or 3.8 litre car. I note that The Australian Jaguar magazine [edition 91] quotes
MK1 2.4 $1000 to $20,000 MK1 3.4 $1000 to $25,000
MK2 2.4 $ 2000 to $20,000 MK2 3.4 $3000 to $30,000 [3.8 $3000 to $40,000+]
The April edition of Australian Classic Car is a little more circumspect in quoting top price for a MK1 2.4 as $11,500 and a MK2 2.4 as $14,000 while the top price quoted for a MK2 3.8 is $29,000.
Better Brakes? Having faced up to the fact that a 2.4 litre sedan will never be worth as much as a 3.8 you still have a number of options if you feel that you want more performance. However before we go down that route there is one important aspect to remember particularly if you are dealing with MK1 sedans. It is no use making it go faster if you can’t make it stop. The drum brakes on a 2.4 sedan are “adequate” but on the MK1 3.4 are generally acknowledged as being at or even getting beyond their limits. If you are going to increase power then you should give serious attention to the brakes. There are kits available to install later series Jaguar disc brakes to the front of a MK 1 and I recommend you get in contact with suppliers such as Geoff Widdicombe , GBC, Jag World, British Cat Components and Don Milliner all of whom advertise in this magazine for advise, expertise and general cost of this conversion.
Heart Transplants Some of your power options include an engine heart transplant. If you can access a MK1/2 3.4 or 3.8 engine this is a simple and relatively cheap way to go. Unless the chosen transplant engine has really major problems you should be able to fully overhaul it for somewhere around $2000 to $3,000. If you are a do it yourself person you may get out of it much more cheaply. 4.2 motors are quite plentiful however you may have problems in sorting out engine mounts pulleys and other accessories.
I note what looks like a late model [4 litre?] fuel injected engine under the bonnet of a MK 2 in edition 91 [page 69] of Australian Jaguar. I also knew of a MK 1 with a Holden 179 engine, which lived in inner city Brisbane and regularly towed a trailer to the family weekend farm. Jaguar also put a V8 Daimler engine into the MK 2 body shell and called it a Daimler 250. From that point of view your options are pretty open.
Staying with the 2.4 and originality. A relatively cheap way to go is to look at the upgrades available on the 2.4 engine. Jaguar did offer a number of options in both manufacture and aftermarket products so you could make a number of improvements and modifications and still be “original”. It is worthwhile noting that Jaguar quotes the following HP figures of MK1/112 hp: MK2/120hp and 240 saloon/133hp. The 240 was fitted with the 13/4 SU carbys.
If you have one of the very early 2.4 engines it has small valves and as such the head is hopeless for any upgrade in power. A “B” series head with the larger valves and higher lift camshafts is needed. These are amazingly plentiful once you start looking as the majority of later 3.4 motors had them. Experts talk about “C” and “D” heads but they are rare, expensive and probably an overkill on a 2.4 engine.
Along with the B series head a MK1 or MK 2 3.4 intake manifold and SU HD 6 1 ¾ inch carburettors along with the starting carby are needed. These should preferably come off a MK1/2 3.4 or 3.8 engine. That will allow you to use standard plumbing for the cooling system and standard carby linkages. Another possible source is the S type sedan. The original 3.4/3.8 engines used a thermostat to control the starting carby. Most owners have modified them with a switch under or in the dash panel to allow direct control of the starting carby. One cunning place to fit such a switch is a push off/pull on switch fitted in the bracket just above the bonnet release knob and operating in a parallel direction with the knob. Somebody had done this to my MK 1 “hotrod” and you cannot see it or find it without being in the “know”.
Finally the crummy little narrow single pipe exhaust system used on the 2.4 should be replaced with the 3.4/3.8 dual exhaust system or at least a much-enlarged single pipe system. Note that the 2.4 exhaust system will not fit a 3.4/3.8 engine, as the increased height from below the vehicle to the exhaust manifold becomes a problem. There is about a 2 to 3 inches difference in pipe length due to the deeper motor, higher block and increased depth to get below the vehicle floor.
Jaguar also recommended 9:1 pistons. In view of the current environmental lobby and phase out of leaded petrol this may not be the best way to go. 8:1 seems to be about the limit for compression ratio with modern fuels and old engines.
With all of the above modifications including the 9:1 pistons it is suggested that an overall increase of about 45 Hp was possible. This would put the modified 2.4 engine at about 157hp which is pretty much the same as the original 3.4 engines rating of 160 hp as fitted to the XK 120 and MK7 sedan. Even without the higher compression pistons 20 to 30 HP should be achievable and would make a significant improvement to the performance of a 2.4 saloon.
Cooling the engine. I have had queries as to whether the 2.4 radiator would need modifying. As yet I have not been able to establish any difference between 2.4 and 3.4 radiators. I would suggest that if you have a marginal 2.4 engine that tends to overheat you would have problems if you did anything to increase performance. It would be best to have the radiator cleaned at least. John McDonald from Stafford Radiator Service who advertise in this magazine assures me that standard cores are readily available and special high capacity cores can be ordered for cars with specific problems such as air-conditioning added on etc.
If you have an early MK1 2.4 with a cast alloy four blade fan remove it and replace it with a late model MK 2 multiblade fan. The 4-blade fan is hopeless in the Qld. environment even when the engine and radiator are in perfect order.
Getting rid of the Slushbox [Automatic Gearbox] As previously mentioned the DG automatic gearbox is does waste a significant amount of power and ultimate performance will only be gained by replacing it with a manual gearbox. This is serious stuff as there are numerous areas that need to be addressed in such a conversion. [Been there - done that]
The simplest approach is to get a MK1/2 manual [moss] box and bell housing. However an engine previously used in an automatic car will need a flywheel and clutch plates. A slave cylinder, a different [single piece] tailshaft as well as a manual pedal box setup with clutch master cylinder and flexible lines will also be required.
There are also a number of other Jaguar manual boxes available however the gear lever position might take some working out as well as gearbox mounts. Don’t forget or overlook other conversions such as the 5 speed Toyota Celica box conversion developed by Ron Moore.
Differential ratios I refuse to enter this minefield. There are undoubtedly experts out there who may be able to assist. Limited slip differentials and their ilk sound great and have their uses but I think you need specialist expertise to get involved in those areas. If you have a diff that works OK for you then leave it alone. If you need some better ratios after a heart transplant the find out what original type was fitted to a 3.4 or 3.8 vehicle and use that as a starting point.