Jaguar MK1

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Do you drive this great classic or are thinking of buying one? Here’s how to ensure that you get the best out of your car for years to come

Jaguar’s Mk1 turned 60 this year and has never been so highly regarded. For decades it was overshadowed by the ‘superior’ Mk2 but now it’s the earlier saloon that’s the most prized. A slightly simpler car to the similar Mk2 but parts are specific to the earlier model and aren’t as easy to obtain. Our thanks to expert Ken Jenkins who helped with this feature

ENGINE OUTPUT

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Shed loads of tuning gear around (see last month’s issue) including official factory parts which raised 2.4 to 119, 131 and 150bhp although post ’66 ‘240 top end’ uprate (133bhp) suffices but exhaust needs re-routing. Most start with 3.4 or better still 3.8 unit. Cheap tweak is to fit XJ6 S3 head and cams but you need to match manifolds. Ultimate is fuel injection and modern ignition mapping but it costs thousands; fit a good electronic ignition and have it set up correctly by an expert.

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Once high tech, the XK now holds few fears and needs few special tools. Overheating worries mostly ungrounded if cooling system is well maintained with correct anti-freeze mix; Evans’ Waterless Coolant is a good ploy, too. Tappets must be just audible and any resetting is best done with head off as part of a decoke. Even if you’re not after more power, fitting later ‘240’ head, cam, exhaust and carbs worthwhile as original Solex units wear out and are very expensive to overhaul.

BOTTOM END

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All XK units have a fair bit of stretch in them, even 2.4 can be taken out close to 3-litres using XJ6 2.8 crankshaft. According to Ken Jenkins 3.4 block can be taken to 3.9 and makes nice unit while torquey 4.2 has scope for 4.5 and 4.7-litres but specialists say it’s rarely worth the trouble and expense. Modern ‘spin-on’ oil filter is popular mod but be careful as some (such as MGB conversion) isn’t up to the task. Head bolts are now tightened to 60lb to improve gasket longevity.

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The bottom end is pretty tough although major tuning may require stronger pistons and con rods to withstand higher revs – remember 2.4 has smaller block. Oil pressure should be 40lbft at 3000rpm (min). Bottom timing chain renewal is difficult for DIYers. Rear crank oil seal is notorious leaker (some owners top up mid way between min/max to reduce loss) but there are modified types available now although replacement still demands crankshaft removal.

FRONT SUSPENSION

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Mk2 axle assembly has far superior geometry to the Mk1 so it’s a good idea to replace entire assemblies for Mk2 for starters before considering uprated dampers, springs and bushes. The 420’s complete suspension beam yields superb Varomatic PAS. Drum braked cars can easily be fitted with Jag discs or use aftermarket kit. Another benefit of 420 axle are better brakes.

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Mk1 used certain parts not seen on earlier Jags or Mk2 but you can fit XJ40 lower ball joints to good effect. Watch ride right as settled suspension can ground sump in some cases and when selecting springs, remember they differ across the Mk2 and S-type ranges. Worn suspension bushes can be polybushed for as little as £25 a go and do the same for the anti-roll bar bushes and eyelets.

CARBURATION

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You’ll rarely see triple carbs on saloons due to the limited space available without some butchery – it’s not needed anyway. Coombs largely stuck with SUs (1.75 or 2in depending upon tune) as it found Weber DCOEs of little benefit. The ultimate is fuel injection (an XJ6 system can be adapted or go aftermarket along) with mapping of the fuel and ignition systems but it’s the thick end of £2000, the results are said to be impressive, mind. You can’t fit SUs on 2.4 without the proper 240 head and manifolds.

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An old and effective trick on the auto choke system – especially if playing up – is to wire in a simple cut out switch to enable a manual override. As we alluded to earlier, the Solex units on 2.4s are a lot dearer to overhaul than SUs and it’s worth fitting the ‘240’ spec top end for the SUs. While you don’t need the head and cams it helps. A session on a rolling road with an XK expert to fine tune the cars and timing under load can really pull out hidden power on a standard XK engine as they vary somewhat.

TRANSMISSION

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Overdrive is essential on any Jaguar (420 combo slots in nicely) but if you want a proper five-speeder then the Jag/Rover unit from the 1970’s is tailor made for the job with good ratios, too. Another option is a Toyota Supra gearbox with nicer ratios and a great change quality. All Mk1s came with slow old Moss gearbox but the post ‘65 Jaguar unit can be fitted, if not already done, although it needs later bellhousing and stronger propshaft. Lighten heavy old flywheel, too.

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Although the Jaguar unit is much slicker than the earlier Moss type, all are cumbersome in the absolute sense but you can improve matters by draining the old oil and replacing it with a modern synthetic (speak to a Jag expert first on best type). Overdrives can play up but so long as the oil is clean, troubles usually stem from faulty electrics and its solenoid. Both types of automatic gearboxes employed are pretty rugged.

REAR SUSPENSION

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Biggest criticism is the narrow rear track. Owners used to reverse the rims to widen it or fit Mk2 axle but cutaway spats will be needed. Alternatively, MWS International market bolt-on spline hubs for the rear, which effectively increases track by half an inch. When used with off-set competition wire wheels, the track is about right. Uprating is usual dampers and springs route.

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Leaf springs settle but easy to right. Handbrakes notoriously ineffective but bad adjustment hardly helps; trick is to free it before disconnecting cable, make adjustments at the calliper end using a four thou feeler as a guide between disc and pads, then adjust the cable. Bear in mind geometry changed on 3.4 in 1958 along with change to Girling dampers.

DIFFERENTIAL

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A wide range of axle ratios were used across the Jag ranges depending upon engine and transmission so you can pick one for better pull or more relaxed cruising. Fitting a Mk2 axle not only broadens track but gives you the option of a limited slip diff taken from the 3.8. Poly bushing is a good idea to keep axle in check; Superflex types cost just £12 from Viamoto, for example.

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Rear axle is sturdy affair but watch the ratios if you need a replacement; overdrive cars (Mk1 and Mk2s) used a lower axle ratio for better pull in for example and the speedometer may need recalibrating. LSDs are dear to repair. On all, check the axle location and security as it can move and alter the rear wheel alignment and effect handling, plus catch the fuel tank.

BODY & CHASSIS

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While some panels and trim were carried over to the Mk2, there’s significant differences between the pair and panel supply isn’t so plentiful either. Leading Jaguar expert Ken Jenkins restores bodies and adds extra beef where needed, like at the ‘crow’s feet’ by the crossmember, suspension points and rear bulkhead. If you’re worried about a hot running engine and need added cooling, then why not try a Coombs bonnet louvre mod?

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All old Jags are rot boxes and unrestored examples are likely to be full of filler as it can easily cost five figures to make a shell like new again. The main areas to keep an eye on are the box sections, inner wings, and floors, front and rear bulkheads, and the infamous ‘crow’s feet’ which is welded to the front valance and the crossmember. Widening of the track means the rear spats (which rot) will have to be discarded.

INTERIOR & TRIM

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There’s a lot of wood and leather to restore – perhaps more on the Mk1 and like the bodywork, few items are interchangeable. Reclining seats were never an option even new; some used to make brackets up to tilt seat but there were competition bucket seats when contemporary, or you can graft on perches from the Mk2, XJ6 (S3 types best) and even later Jags.

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Apart from the design, virtually everything was different to the Mk2, including the dash instruments, which were more akin to XK/Mk VII saloon designs which can be utilised after altering. There’s even more wood to preserve in a Mk1so like the Mk2, expect to face big bills for a full-on resto: £2000 for the dashboard alone. Don’t overlook poor brightwork as re-chroming bumpers costs £400 alone!

AND ANOTHER THING…

Be careful altering a good Mk1 as values are soaring, outstripping Mk2 values, meaning originality will increasingly count in the future. There are subtle differences in design meaning that not only are Mk2 parts not directly interchangeable (such as suspension parts, for example) but nor are components from XK sports cars or the large limos even though they were both produced alongside the Mk1.