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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

An evolution of the original 100/4 the 100/6 featured six cylinder power. There’s an army of specialists for parts and repairs and parts availability as almost as good as a Jaguar. Names worth knowing are AH Spares 01926 817181, A Head 4 Healeys 01788 565000, Bill Rawles Classic Cars 01420 564343, Rawles Motorsport 01420 23212, JME Healeys 01926 499000, Denis Welch Motor Sport 01543 472214, DM Classic Cars, Murray Scott Nelson 01723 361227, Classic Cars 01772 614637, UK Healey Centre 01924 899007 and the Austin Healey Club 0116 2544111. Get ringing!

1 ENGINE OUTPUT

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Early BN4 cars had a paltry 102bhp – for ‘57 a six port head spelt 117bhp, seven down on first ‘3000’. Same tuning rules apply (head, SU or Weber carbs) but less power, but you should still see around 160bhp. Logically, unless originality is paramount it’s best to fit ‘3000’ engine which yields up to 150bhp as standard. Alloy heads add power and save weight but cost £3300 alone!

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As you’d expect these beefy sixes are very strong even if high oil consumption is typical. As engines were designed to use a heavy monograde, keep to a 20W/50 or 60 brew. Oil pressure should rise from about 10psi at idle to 50psi when running fully. Overheating problems are usually normally nothing more dire than a poorly maintained cooling system. An uprated rad and a later 3000 blade fan (or quieter AH Spares five blader for £42) usually does the trick.

2 BOTTOM END

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The 2.6 can be enlarged to 2.9 to match the 3000 but it’s a bit risky say experts. In contrast the larger ‘3000’ lump can be stretched to 3.3 or even 3.5-litres and although it’s expensive work, it is certainly effective in terms of torque. Lighter steel flywheels (or you can have your existing one skimmed by a machine shop) improves throttle response and there’s also performance steel crankshafts and con rods for highly tuned units, albeit chiefly for racing purposes.

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These engines seep oil, usually at the rear but a rear crank seal kit (under £50 from AH Spares) cures it. If the engine is beyond economic repair, C-series blocks can still be found, since these m were fitted to BMC saloons of the time,
such as the Westminster albeit detuned.
Other parts such as upgraded cylinder heads,
camshafts, exhausts, carbs etc are available from specialists such as Denis Welch, Rawles, AH Spares and so on.

3 FRONT SUSPENSION

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Best convert to a tailored telescopic front suspension using Spax adjustables (around £450 from A H Spares) which along with poly bush kits makes a world of difference. You can also go further with upgraded anti-roll bars (different thickness available). If you stick with lever arms you can save money by just fitting new valve units for around £25 a pop (A H Spares) but it depends how worn they are – and it’s over £200 per side if you want new ones.

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The standard wishbones and coil springs, plus an anti-roll bar set up isn’t bad for most road driving if in good order. If you want to retain lever-arm shock absorbers, you can buy upgraded ones, which will keep the original look but still improve handling. If you do, opt for quality types as against cheap short-lasting recons. AH sells quality reconditioned units from £53. Front damper mountings prone to working loose and those lever arm dampers leak.

4 STEERING

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There’s a number of power steering mods which include a dedicated rack and pinion kit from Rawles Motorsport which costs a more than £5000 fitted or an electric (MGF/ Peugeot hybrid we understand) kit for the existing set up at half the price. Even cheaper are special bronze thrust washers to reduce friction from AH Spares at under £35. Welch manufactures boxes to higher specification than the originals and can also supply a high ratio version, although this will make the steering heavier.

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New steering boxes are hugely dear – over £1500 – so consider having yours rebuilt from ICS (see Trade Talk feature in this issue). A normal amount of slack is usual and mostly can be adjusted out. These cam and peg boxes frequently leak, but check that the box isn’t running low on oil. If the steering feels loose it’s probably because of worn bushes and kingpins, the latter should have been greased every service. As the running gear is essentially Austin, you may find cheap parts at an autojumble.

5 BRAKES

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The cars initially came with drum brakes, but you can upgrade to discs fairly easy, either with a nut and bolt kit or using stock 3000 parts. Competition pads and callipers along with, braided hose kits, to help eliminate brake sponginess, are also available
if you want to go further. You can also add new Delphi brake servos (£225 from AH Spares) to ease right foot pressure and that’s a mod we’d recommend on any model.

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If properly maintained, the drum brake system suffices on the road, especially if you’re not a heavy driver although harder linings from Mintex or Ferodo, along with the aforementioned brake servo is a wise step. If you do go ‘3000’ discs and want
to uprate further, Lotus Cortina callipers and pads go a treat.

6 GEARBOX AND OVERDRIVE

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The transmission is strong enough to take 200bhp but tougher race-proofed overdrives at £1450 and straight-cut gear sets at £900 available. There’s a five-speed kit using a Toyota Supra unit. With a slicker change and better intermediates it transforms the car. A Head For Healeys and Rawles Motorsport both produce fitting kits that ensures the gear lever location is unaltered but depending where you go it’s an expensive conversion of at least £2500.

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The gearbox is a four-speed unit taken from the Austin Westminster, with overdrive. First and reverse, have no synchromesh and suffer from wear. The overdrive works on the upper two ratios and any problems are more likely to be due to faulty electrics rather than hydraulics. You can also fit an upgraded overdrive kit, which will increase the oil capacity in the piston and cut engagement times (almost £350 from AH Spares).