Aston DB4-6

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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

Given their sky-high values, the thought of tinkering with an Aston Martin at home sounds insane. That said, there’s nothing high tech about cars which are now 50 years old, and while you may wisely prefer to leave major servicing and repairs to an Aston expert, their short 2500 miles maintenance intervals mean it’s worthwhile that you, the owner, keep on top of things. Here’s how to give your Aston an advantage over all the others!

1. Body & chassis

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Modifying a DB? You’d be mad to and spoil the car’s originality although certain alternations, such as a period racing look can be acceptable. The DB6 Mk2 features slightly flared wings to accommodate the larger tyres; if during a rebuild your car requires replacements then it’s probably doable fitting them as is altering the inner wings to accept the Aston V8 just like the factory did during its long development.

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This is where the money lies as rebuilds can be horrendously expensive and all DBs can rot badly; bulkheads, pedal box area, sills, jacking points, chassis frames and outriggers plus floors, which can be more suspect on Volantes. Aluminium doesn’t rust of course, but corrosion caused by the interaction of the alloy outer panels and the steel Superleggera skeleton structure is something you need to keep a constant watch on.

2. Bottom end

Mod

If the block needs new cylinder liners, it makes sense to take it out to 4.2-litres and many Aston specialists do this as a matter of course during a rebuild as it makes for a much nicer unit and what the factory did for racing. The mod costs little more than using standard pistons and liners. You can go further, up to 4.7-litres, but it’s not necessary for road use. Oil pressure should be 90lbft @ 3000rpm and it takes 23 pints of 20W/50.

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Biggest problem with the straight six is sludging up of the iron cylinder liners, especially the rear two, which can lead to major overheating; only cure is a head off repair and it’s imperative that an Aston expert only tackles the job to prevent damage to the block. Aston used to recommend ‘Barsleaks’ to stop leaks which hardly helped matters. Always keep the antifreeze fresh and at the correct strength.

3. Engine output

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Tuning the straight six engine can be surprisingly cost effective during a rebuild. Aston’s power figures were optimistic so after cylinder head and Vantage C-type camshaft upgrades, 300bhp is genuine and there’s more if you also opt for the popular 4.2-litre enlargement and even 450bhp+ in 4.7-litre racing tune. During a decoke, fit larger Vantage valves, a relatively inexpensive mod. There’s not a lot wrong with triple SUs so don’t instantly think of fitting Weber DCOE carbs.

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Fixing up triple Webers can cost £1000, with a decoke and light pep up six times this although – along with a rolling road session – can yield much better pep. A full engine overhaul on the ‘six’ can cost as much as £25,000, which is dearer than the V8! Fitting a Jaguar 4.2 XK alternative was not uncommon and much cheaper but you’ll lose out (in residual values) far more than you gain short term. Uprated cams cost around £1000 each and usually lead to increased noise but more go.

4. Suspension

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Most will by now have ditched the Armstrong Selectaride adjustable rear dampers in favour of (lever arm) replacements such as Konis. You can convert to modern telescopics although it’s mainly a track ruse because it hurts the car’s originality. Harvey-Bailey produces a complete upgrade kit for less than £2000 while Rikki Cann and Astonparts.com have similar cheaper alternatives. Get sensible advice before polybushing.

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If the Selectarides are still fitted (they are also prone to leaking), most specialists set them to the hardest setting and leave them like this. These Astons are heavy beasts and this takes its toll on the springs and dampers. If, when reversing, the tail slightly rises, it points to worn rear trailing arm bushes or may have even become detached. At the front, watch for broken steering rack straps and seized wishbone inserts.

5. Transmission

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Apart from the DB4, all featured five-speeds as standard; earlier DB4 can be retrofitted with either a stock Aston ZF or a more modern alternative. Another ‘today tweak’ is six-speeds care of a BMW transmission although it’s expensive and you are further advised to change the axle ratio at the same time. Autos are rarely liked but again you can fit a modern four or fivespeed self-shifter if you don’t want a manual gearbox; try Aston Workshop.

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The ZF gearbox is pretty robust and a good thing too as it usually costs £2000 or more to fully overhaul. Limited slip differentials are known to be quite noisy and while a certain amount of wear and play can be adjusted out, it’s a characteristic. Another trait is a lorry-like clutch action although Aston specialists can reduce the load significantly by fitting a modern diaphragm clutch assembly. Worth doing come replacement-time.

6. Brakes

Mod

There is a lot you can do to this all disc set up, starting with normal EBC Green Stuff or Mintex uprated pads. For the DB4, Trinity Engineering markets improved brake callipers along with larger front discs to replace the original Dunlop design. For the DB5 and DB6, the best mod can be fitting DBS V8 parts and the factory’s brake servo upgrade as well as the attendant master cylinder which in all costs some £1800 – but it’s superb says Trinity.

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The all disc set up was considered brilliant in its day and even now, if in good order, is entirely adequate for the road. Rikki Cann suggests a good service along with Castrol SRF brake fluid; £45 a litre but it’s the business he says. DBS V8 brakes keep the original theme and work well. AP sells a full brake kit upgrade costing £3000 so it’s only viable if system needs a total rebuild or you want best brakes.

7. Trim and details

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Apart from retrims, specialists find owners want to specify some bespoke enhancements such as modern ICE units (with secluded speakers), improved power windows, the addition of central locking and quality alarms which automatically work them once activated. Air con is another popular fit including better sound insulation. Or how about LED interior light conversions?

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All Aston parts are very dear. Take the period washer bottle which, if leaking – promoting rust in the engine compartment – costs £80 alone to renew. Chromework restoration runs into thousands and running a de-bumpered racer look will devalue most DB models. A trim refit will never be a cheap job but certain switchgear and Smiths instruments etc came from rival carmakers.

8. Electrics

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As exotic as they are, DBs are really old school so only sticklers for originality will wish to keep the car standard. A modern electric fan in conjunction with an uprated radiator will quell any worries here. Uprated starter motors, alternators and headlamps (including LED systems) are worthy fits but you’ll probably need to have the car converted to negative earth first.

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We’ve touched upon replacement starters and generators which are sensible fits if they need replacing – likewise PAS for a modern electric alternative. Convert to electronic ignition as it’s one of the best enhancements you can make, improving pep and reliability. Aston specialists seem to favour ‘123 Distributor’ set up incidentally.

9. Steering & tyres

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Power steering only fitted to DB6 onwards. Trinity suggests the EPAC electric system but you can also try EZ or Lite-Steer of Sussex. In fact, some Aston experts reckon if the PAS needs replacing, it’s best to go modern. Tyres are a matter of taste but Avon CR28s appear to work well; 185 section on the DB5 and DB6 and a 205 size for the MkII.

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DB6 MkII has slightly flared wheel arches. Some owners fit later larger DB6/DBS rims on the earlier car but usually run into fouling problems and some specialists reckon they don’t ‘look right’ even if they fit. Polybushing should be done after seeking advice as they can spoil the car’s refinement although beefing up standard anti-roll bar ones is okay.

And another thing…

Before modifying your DB speak to an expert because while originality counts and preserves their values, certain improvements using accepted Aston mods can actually enhance residuals. One leading expert, RS Williams, is a staunch advocate of using modern technology, so long as the car still looks original.