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Jaguar S Type

Published: 28th Jun 2011 - 0 Comments - Be the first, contribute now!

Jaguar S Type

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All Models including the 420


All are twin-overhead camshaft, in-line six-cylinder types 3.4: 3442cc 210bhp 3.8: 3781cc 220bhp 4.2: 4235cc 245bhp

Valve clearances

Inlet 0.004in; exhaust, 0.006in. (cold); the gaps are measured using feeler gauges placed between the back of each cam and the appropriate tappet. Adjustment is by selective shims. It is advisable to check the clearances every 12,000 miles; re-setting the gaps is a major head-off operation, not for the faint-hearted and best carried out along with a full decoke.


Engine oil: For maximum engine life, ideally change oil and filter at least every 3000 miles or annually (whichever comes first). Ensure that oil filter assembly components are correctly installed on re-assembly (consult workshop manual for sequence). Use premium quality, SAE15W50, 20W50 or 20W60 oil. Please dispose of old oil in environmentally friendly manner – local councils provide waste oil collection points. Drain/refill capacity, approx: 13 pints (7.38 litres) Manual gearbox oil: Check oil level at least every 3000 miles or annually (whichever comes first); investigate need for frequent topping-up. Early cars with synchromesh on second, third and top gears, use engine oil. Later cars with all-synchromesh gearboxes, use SAE90 EP gear oil. Every 12,000 miles (approx.) drain old oil after a long run, and re-fill with fresh lubricant. If overdrive is fitted, overdrive unit’s oil supply is shared with gearbox; to drain, remove plugs in both gearbox and overdrive unit. Every 12,000 miles remove/clean gauze within unit (accessible when drain plug is removed). Capacity: 2.5 pints (1.42 litres), or 4 pints (2.27 litres) if an overdrive unit is fitted. Automatic transmission fluid: Check fluid level at least every 1000 miles/monthly (whichever comes first). Be scrupulously clean when checking fluid level and when topping-up. Torque converter must be full of fluid when checking level: First, with handbrake firmly applied, engage ‘P’ and run engine. Apply footbrake and engage ‘L’; run engine at 800 rpm for approximately three minutes, then return to normal idling speed. With an assistant applying the footbrake, and with engine still at tickover, withdraw dipstick, wipe clean, then re-dip and withdraw again to check level. Top up with automatic transmission fluid if required (DO NOT overfill); difference between ‘high’ and ‘low’ marks on dipstick equates to approximately 1 pint (0.57 litres). Change transmission fluid approximately every 12,000 miles; capacity 15 pints (8.52 litres). Final drive oil: Check oil level at least every 3000 miles or annually (whichever comes first); investigate need for frequent topping-up. Use SAE90 EP hypoid oil. Renew axle oil every 12,000 miles (approx.); drain old oil after a long run (so that it flows more easily), and re-fill with fresh lubricant. Capacity 2.75 pints (1.56 litres). Steering/front suspension: Every 1000 miles, re-lubricate all greasepoints using multi-purpose, lithium-based grease. There are nipples on: Upper and lower swivels (assuming original types are fitted), steering rod ball joints, and steering idler unit(cars with non power-assisted steering). Front and rear wheel bearings: Every 5000 miles, re-lubricate bearings with grease specifically stated as being suitable for wheel bearing use; grease nipples are provided. Steering: Cars without power-assisted steering: Check oil level in steering box approximately every 3000 miles/annually (whichever comes first). Note: Filler plug has hexagon head; don’t confuse with externally threaded rocker shaft adjuster screw. If necessary, top up with SAE140 EP oil. Car with power-assisted steering: Check fluid level in reservoir every 3000 miles or annually (whichever comes first); use automatic transmission fluid to top up as necessary. Renew filter in reservoir every 24,000 miles. Wire wheels: At least every 12,000 miles/once a year (whichever comes first), apply grease to hub/wheel splines to minimise wear on them. Other aspects: Every 3000 miles, re-lubricate handbrake operating linkage and check its operation.

Fuel system

Every 3000 miles or annually (whichever comes first), examine all fuel system pipework and check/top up S.U. carburettor dashpots with SAE 20 oil. After valve clearances and all ignition settings have been checked/set, and with engine fully warmed up, re-adjust carburettor mixture/idle speed settings (use proprietary do-it-yourself equipment for synchronising carburettors, and proceed in conjunction with workshop manual). Aim for a tickover speed of approximately 500-650 rpm. Clean/lightly re-oil gauze air filter elements every 5000 to 6000 miles; renew paper types every 10,000 to 12,000 miles (or sooner if visibly dirty). If an oil bath type air cleaner is fitted, remove top cover, lift out gauze filter and clean in paraffin, then allow to dry. Empty out oil/sludge from filter housing, wipe dry then re-fill with fresh engine oil to level indicated by arrow on side of housing; re-fit gauze filter and housing lid. Clean fuel filters approximately every 10,000 miles or annually, whichever comes first (include tank filter, accessible after removing drain plug – do this only when fuel level is very low!).


At least every 3000 miles or annually (whichever comes first), carry out following operations: Examine front and rear brake pads and discs, also separate handbrake pads. Inspect also brake pipes/flexible hoses and master cylinder. Renew any ailing components AT ONCE. AVOID INHALING DUST FROM PADS - MAY CONTAIN ASBESTOS. Assess handbrake operation and re-adjust cable length if necessary (consult manufacturer’s literature for full details).DON’T over-tighten cable or brakes will bind. Check tightness of caliper securing bolts; ensure locking wire is fitted and secure. Inspect brake fluid and check level; overhaul system if fluid is cloudy. Every 6000 miles/annually (whichever comes first), clean brake servo filter; rinse in methylated spirits, allow to dry, lubricate in clean brake fluid and then re-fit. At least every 24,000 miles/two years (whichever comes first, change brake fluid regardless. Note: The inboard-mounted rear brakes are notoriously difficult to reach. If the rear axle/suspension assembly is ever removed from the car, it is a good idea to fully service the brakes, and replace leaking oil seals, at the same time. Check especially for seized rear caliper pistons (more likely on cars which are used infrequently AND NOT TO BE CONFUSED WITH A POOR WORKING HANDBRAKE), also for oil contamination on the discs/pads.


Firing order: 1-5-3-6-2-4 (No. 1 cylinder at REAR). Spark plugs: Champion N5 or equivalent (L7 for 7:1 low compression ratio engines). Later 3.4/3.8 litre units, Champion UN12Y or equivalent. 4.2, Champion N5 or equivalent (later specification, N11Y; consult Jaguar specialist for correct type). Gap 0.025in. Check/clean every 6000 miles or annually (whichever comesfirst); renew regardless every 12,000 miles. Contact points: Gap 0.014in. to 0.016in. corresponding with dwell angle reading of 35 +/- 2 degrees. In each case, check/clean points every 3000 miles or annually (whichever comes first); renew regardless every 6000 miles. Distributor cap, rotor arm and high tension leads: Every 3000 miles, clean and check condition, ensuring that all connections are sound. Distributor – mechanical aspects: Every 3000 miles, remove rotor arm and apply a few drops of engine oil to moving contact pivot, distributor shaft/cam bearing and mechanical advance mechanism (via holes in distributor’s baseplate). SPARINGLY apply grease to distributor’s cam. Timing - examples (static; refer to timing marks on crankshaft pulley damper and timing case): 3.4 and 3.8 litre: 7:1 compression ratio, 0 degrees (TDC) 8:1 compression ratio, 7 degrees before top dead centre (BTDC) 9:1 compression ratio, 5 degrees before top dead centre (BTDC) 4.28.1: compression ratio, 9 degrees BTDC; 9:1 compression ratio, 10 degrees BTDC (mark on crankshaft damper).

Cooling system

At all times, use quality anti-freeze mixture containing corrosion inhibitors. Every 3000 miles/annually, inspect radiator, all hoses and water pump/fan. At least every three years, drain system and reverse-flush prior to re-filling system with fresh anti-freeze solution (observe dilution recommendations of anti-freezemanufacturer – printed on container). Capacity, including heater: 22 pints (12.50 litres).

Best Mods

  • Apart from a thorough service, one of the best tune ups you can give the XK engine is a session on an engine dynometer to see if the ignition and carb settings can be improved over standard settings.
  • Electronic ignition is worthwhile. Luminition has been a popular upgrade for a few years and does away with the points for maintenance free motoring. Prices start at £150 from Classic Spares (01992 716236)
  • It is a myth that Jaguars suffer from poor cooling and will overheat. If everything is in top order, then all should be well. However, in some marginal conditions it helps to have a bit in reserve. An uprated radiator is a wise step.. Not only is the cooling enhanced, but with the engine driven fan removed, a few bhp can be gained. Prices start around £375.
  • Polyurethane suspension bushes have become popular; they’re easy to fit, long lasting and more efficient. In some instances though, they can give a jarring ride which is what the S-Type is all about against the MK2. Prices start at £22.50 for a top wishbone kit. Better dampers offer tremendous improvements. Try Koni or Gaz, starting at £46.
  • Front suspension can be greatly improved if you use later 420 uprights to gain superior three-pot callipers. Avoid XJ type power steering rack conversions, seek out complete 420 front beam and use the Varomatic steering box, it is very good still. Don’t forget to use the right springs to go with the set up though.
  • The 3.4 engine is already strong but could be better with straight port cylinder head and E-type camshafts. For ultimate performance, use a 3.8/4.2 engine with straight port cylinder head and a pair of 420 (2in) carburettors. Triple carbs can be used, but clutch master cylinder has to be altered to clear third carb.
  • Want more ccs.? Okay so the 3.8 is a natural fit over the 3.4 but without doubt the 4.2 is the most sensible pick if you’re engine swapping. It can be taken to around 4.5-litres but even in stock guise works well with the later fuel injection as on S3 XJ6s. Mind you fitting EFI is a hassle. Thankfully even on carburettors it is fine, especially with sorted and fully mapped ignition grafted on (expect to pay around £1500).

Top Tips

  • It pays to check the ride height annually. The front springs are known to settle, leading to worsening ride and an even heavier steering. If really bad it can ground the sump on sleeping policemen. Uneven tyre wear with excessive inner scrub is a clue.
  • If you need new springs and are searching the auto jumbles, remember that the car uses different springs to the lighter MK2 and the Daimler V8.
  • Still at the front, the front suspension bushes wear quickly and apart from wandering can display itself as a knock over road bumps.
  • The IRS suspension is the same as employed on theE-type and its myriad of bushes deteriorate and ruin the car’s poise and precision. But the front suspension is just as susceptible and lets go in the same way and are often overlooked.
  • The handbrake is always a bugbear on old Jags and for it to work even remotely satisfactory then all the linkages,pivots and the cable compensator need to be in tip top shape. A check and going over before MOTtime is very wise if you want a straight pass…
  • If the exhaust is up to OE spec and originality then it will have some short flexible sections. These can work lose and lead to a blow.
  • The engines, once so advanced and complex, are now old hat although DIY work is still heavy duty. Especially if you want to remove the engine. A clutch change is a major job as the front cross member has also to be dropped. To tell the truth it’s a job best left for the specialist unless you really into DIY.
  • Over-silent tappets indicate that the valve clearances have closed up and need re-shimming ( a job thatrequires a micrometer). Again perhaps a specialist is best to do this and as the cam and head have to be removed then it’s best to budget for a complete top end overhaul at the same time. If the timing chains are weak (there is decent adjustment to be fair) then consider this too, although the bottom one requires dropping the sump – which is akin to a major overhaul and a two day job for most folk.
  • However there are ways to change just the top chain (which wears the most) without removing the cylinder head. It’s an old mechanics dodge: break the chain on top of one of the sprockets and attach the new one to it. Wind off the old chain and – so long as you keep it tight on the sprockets – the new one will ‘feed’ in.
  • All gearboxes, even the post-65 Jag unit, are heavy when compared to a modern, although you may be able to improve matters by draining the old lube and replacing it with the latest, lighter transmission oils (speak to a classic oil dealer or Jaguar expert about this first). Overdrive problems are usually electrical although bear in mind that it only operates on top gear!

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