|Achieving Structural Integrity|
|Panel work - Rectification and Replacement|
|Mechanical and Electrical Restoration - General|
|Engine Overhaul and Re-Manufacture|
IntroductionThere are some 5 to 10 thousand parts that comprise an Aston Martin. Some are non-wearing and unlikely to significantly deteriorate as a function of age; but others wear, are subject to corrosion and in the case of electrical equipment prone to failure as a result of degraded insulation and embrittlement. Seals become stiff with age, surface wear occurs and paint and corrosion protection becomes damaged.
Rectifying this deterioration takes time and resource. The quality of any restoration is crucially dependent upon all these hidden components having been restored to a fully serviceable condition or replaced. Only when they are ready can they be reassembled to create a fully restored car.
This section deals with this painstaking reconstruction process.
Achieving Structural Integrity
- The Priority - The first Priority whatever any other work that may be required, must be to replace corroded and damaged structures and chassis to restore structural strength and rigidity. Essential for safety reasons, it is also a must to ensure that the car handles as it should. The chassis forms the heart of all Aston Martins. It is a complex but stiff and strong component and it is far from straight forward to repair and restore.
- Jigging and Alignment – Regrettably, many Aston Martins over their long lifetime have suffered some collision damage. The process of reconstruction includes the removal of major load bearing structures. In doing so, this makes the chassis very flexible. No major restoration should be undertaken without the use of a suitable jig to ensure accurate alignment and prevent distortion during the reconstruction. We routinely use specialist jigs for all of our restorations.
- Problem Areas – Long experience of restoring Aston Martins, particularly DB4 to DB6 and later V8s, has given a clear insight as to where to expect problems. Typical areas we encounter are with sills, front cross members and jacking points and rear suspension mountings. However, even with all that, we find it impossible to be sure just how much damage may have been incurred, particularly corrosion until a significant strip has been done. Many are the cases we have of distortion from collision and now notably, past attempts at structural repairs, some of which are of “extremely doubtful quality”. Other typical corrosion prone areas are under the bonnet closure and valence panels, wheel arches and boot floors. There is no substitute to stripping right back to basics, to jig and rectify the damage properly. Our experience is that major problem areas cannot be foreseen. Hence this insistence on taking the chassis back to basics every time.
- Rectification of corrosion and distortion – The first stage in identifying areas of corrosion is to sand blast the structure so that the true extent of corrosion can be assessed. Clean metal is also an essential starting point for the insertion of new panels and repair sections. Access is also key to enable suspect structure to be surveyed and if necessary removed and replaced with good. All structural welds are seam welds; others on secondary non-load carrying structure are usually spot welded.
- Use of “factory” parts and panels - As we do these restorations day in and day out, we have a substantial level of experience plus a very comprehensive inventory of repair sections, enabling us to reconstruct such components cost effectively to better than the original standard of finish and strength.
- Protection –Every piece of new structure is primed and painted with a tough primer and top coat, both within and without. All corrosion prone structure is then given a comprehensive wax protection, particularly in closed sections, blind panels and those subject to erosion and damp. The comprehensive protection now applied means that structures that typically have needed replacing about every 10 years should now last 20 to 30 years before rectification, given normal use.
Panel work - Rectification and Replacement
- Effects of corrosion on alloy and usual areas of damage – Up until the introduction of the DB7, the pre-dominant material used for all body panels has been aluminium alloy. It is light and generally free of the usual effects of corrosion. However, in the proximity of damp and steel, there is a natural galvanic cell created which then causes rampant alloy corrosion. Corrosion is first seen as bubbling of the paintwork, starting with the odd pin prick and then grows and spreads as the corrosion products multiply. Its products (aluminium oxide) are flaky deposits and white powder. The alloy rapidly becomes porous and seriously weakened. Salt products are a powerful catalyst as they provide perfect conditions for galvanic action. There is in such cases no alternative to cutting out the affected part of the panel and insertion of new metal. Fillers of any description used to cover corrosion will ultimately fail as water and corrosion products distort and then progressively detach the filler from its base. Areas where panel corrosion is most likely to be seen are where the alloy panel is in close proximity to an underlying steel member and/or clenched to it. These are typically:
- The sills, and usually first seen at the back (DB4 to DB6)
- Door bottoms and again DB4 to DB6 are the most prone to this followed by the DB 2 and DB Mk3
- Wheel arches, particularly the rear ones and areas adjacent to the bottom of A and B Posts
- The rear panel adjacent to the boot floor
- The wings in the area close to the bonnet aperture
- Distortion and effects of work hardening of the alloy – All metals suffer from what are termed the effects of work hardening; and aluminium alloy is particularly so. The metal can be shrunk, stretched and shaped and for the grades of alloy used by Aston Martin, is relatively soft. Consequently, most cars have gathered over the years a succession of minor dents and ripples. These can be removed but it is a skilled job and for those who are experienced only with the shaping of mild steel, it requires a different set of techniques and tools. Numerous and over rapid rates of bending will cause the metal to crack. Clearly it is highly desirable to avoid this happening. It is also a fact that an original panel may be already suffering from the effects of work hardening and therefore may need some application of gentle heat to “normalise” it sufficient to allow any necessary reshaping.
- Damage rectification – Shaping, stretching and shrinking can all be done. New metal must ultimately be seam welded to its parent structure. Welding aluminium requires specialist equipment, appropriate fluxes, or use of MIG type welders and a new technique. Whereas steel requires a considerable heat, aluminium melts at a significantly lower temperature. Hence welding aluminium is a highly skilled activity as a continuous seam weld is required and distortion has to be avoided.
- Panel Replacement versus repair - the issues – The key factors surrounding this decision rest on the need for originality, amount of damage to be rectified, availability of replacement panels and the objectives of the restoration. On major restorations undertaken by Aston Workshop, we would generally replace the entire panel work forward of the A-Post and from the B-post to the rear with a totally new panel structure, leaving only the roof as original. Door skins are routinely replaced, and the same, depending on their state, for bonnet and boot. What is essential, however, is that there should be no corrosion present. This approach is best if the aim is to produce perfectly smooth panels. However, for rare cars with bespoke panels, this cannot be done, hence the need for retention of the original panels and for their repair and re-shaping as necessary. Saving old panels does not necessarily save money.
- Preconditions for achieving the perfect finish – It is the policy of Aston Workshop for us to approach the reshaping and recovery of panels to the point that no filler is required to achieve the perfect base for refinishing. If the budget is highly constrained then filler can be used, but as a general rule, it remains possible to avoid such cases in most situations. What is universally required, however, is that the shape and alignment of panels are precisely correct. At this stage, therefore, doors, bonnet and boot are refitted and aligned and any errors in gapping and shaping rectified. A rigorous attention to detail, careful shaping, filing, priming, flatting and guide coating is necessary. This takes time and skill. In summary, the conditions required are:-
- Use of the correct etch primers and primers
- Alignment and gapping has been done for doors, bonnet and boot and any other opening panels
- Perfect shape achieved with no ripples, dents or high spots
- Seams etc are fully sealed
- The car is fully masked as required
- Ensuring absolute cleanliness
All this takes time as well as skill and is one of the key differentiators of the top class restorers and the rest.
Mechanical and Electrical Restoration - General
- Budgets and Timescales – As with the Body work, the key question remains, do we replace or do we recondition. With a heavily budget constrained restoration, it may be desirable to concentrate on restoring only one or two major aspects of the car’s systems, be it engine or suspension. On any Aston Martin, the single most costly item to restore is the engine. For example, a total engine restoration can run up to £30,000 depending on performance options. An unleaded conversion conversely would cost in the region of £5,000 to £6,000. It may be that the decision is taken to just restore the suspension, leaving the engine to be restored at a later date. As always, the restoration objectives and available budget are key determinants in any decisions, as is underlying condition. With a major body restoration underway, there are certain elements which it would be sensible to replace regardless. Examples are wiring looms, brake and fuel pipelines, suspension bushes etc, all of which have to be removed in the first instance anyway. Other components may be replaced on a condition basis only. In every case we always fit new washers, nuts, bolts and studs.
- Planning and control – Long experience of undertaking restorations underscores the critical importance of keeping a firm grip on the scheduling and management of the outsourcing of parts repairs and restoration and on a reliable set of replacement parts suppliers and contractors. To that end we use computers extensively to monitor spend and progress to help ensure the timely and economic completion of your restoration. This together with keen negotiation of the best terms helps considerably to keep costs down and project performance high.
- Choice of suppliers and specialist restorers - We have found that best value is usually obtained with a restricted set of local and national suppliers and specialists, of which first among equals come Aston Martin. We understand the importance of using genuine Aston Martin Parts in your car and we will depart from this only where we have firm evidence that the identical part can be supplied from other trade sources at significantly reduced cost. Over the years we have gained experience as to who consistently provides high quality work and these relationships have been strengthened over time. However, the overall importance of ensuring high quality, value for money and prompt delivery remains.
Engine Overhaul and Re-Manufacture
- General - Aston Martin engines, whatever the model, have an excellent reputation for longevity and reliability when their underlying condition is good, they are correctly serviced and used sympathetically. However, experience also indicates that once one major component shows signs of wear, then it affects other aspects of the engine adversely. In this case, Aston Martin engines are intolerant. Consequently they will start to perform badly and reliability will usually suffer. Fortunately most components were made from excellent materials and unless abuse has occurred, have long service lives. Finally, these engines are designed to be assembled with fine clearances, especially on main bearings. They require expert assembly and hence this is not an operation for the inexperienced. Unless this fitting and assembly are precisely undertaken in scrupulously clean conditions, no matter what new parts may have been fitted, major problems will arise.
- Performance and Reliability – We have available an extensive menu of options for your engine rebuild. It all really depends on what is wanted. As a general rule, because we can exploit components that are in large scale production for other makes, we and all of the other regular Aston Martin engine builders find that it is now cheaper to rebuild an engine with new liners and pistons as a 4.2 than to retain the original 4 litre capacity or in the case of a DB4 the 3.7 litre using bespoke components. From any outward examination the engine remains original and there is a small but noticeable improvement in flexibility and torque. Along with other Aston Martin engine builders, we can increase the capacity still further to 4.5 using the standard cylinder block. For the 4.8 option, cross bolting of the main bearing caps is needed which requires a new cylinder block and the increased stroke a new crankshaft. Each capacity increase brings a significant increase in torque and power, particularly with the 4.8 option. The outline options list is summarised below
- Enhancement options list
- Performance - capacity upgrade to 4.2 litres
- Performance – capacity upgrade to 4.8 litres
- Performance – fast road camshafts
- Upgraded carburation
- Extractor exhausts
- Electronic ignition
- Unleaded conversions
- Peculiarities of Aston Martin Engines – tolerances and the importance of experience – oil pressure – blue-printing – The two most telling indicators of engine condition apart from evidence of oil consumption and general performance are those of oil pressure and temperature. The minimum oil pressure that is usually acceptable is 80 psi at 3000 rpm hot. To achieve this oil pressure, the typical tolerance for main bearing journals is 1.5 thousandth of an inch or 0.05mm. These are fine tolerances and to achieve them, requires very careful fitting. Our experience is that once oil pressure starts to fall below this in service, this may not only indicate worn main bearings. The water jackets around the cylinders are often also “sludged”, causing reduced water circulation and higher oil operating temperatures. Where the oil temperature (if available) and water temperature track each other, then this is good evidence that a significant element of the engine cooling is being done by the oil. This further reduces oil pressure and hence increases the potential risk of wear on the crankshaft. This fact alone helps to explain why it is so important that antifreeze and anti corrosion additives are always kept at full strength. Regrettably, it is next to impossible to fully remove the sludge, especially around the rear cylinders where water circulation is at its weakest. Hence, if for any reason that the crankshaft needs to be removed, it is good practice also to press out the cylinder liners and clean all of the water jacket thoroughly. It goes without saying that an aluminium radiator will provide additional cooling, which is useful in today’s heavy traffic.
- Condition of the block – common defects, defect rectification and making good the effects of corrosion -Cylinder blocks can crack across one or more main bearing webs. The cause is a build up of corrosion products around the base of the liner. These products multiply as the corrosion continues eventually forcing apart the two sides of the block across the affected main bearing web. While this problem remains relatively uncommon, much more common is the erosion of the bottom cylinder liner seats caused by, “you’ve guessed it”, the dreaded corrosion. The sign of this is coolant weeping out of the bleed holes on the side of the block. Blocks badly affected by this will require the liners to be pressed out. Provided the damage is not too extensive, the seats may be recovered using an epoxy based liquid metal which is then machined to tolerance. But in bad cases, new metal will be required to ensure the strength of the block is recovered. Welding any cast metal needs to be done exceptionally carefully; otherwise the block becomes unacceptably warped and becomes scrap. In short it is a job only for the very experienced and equipped.
As a general rule we would carry out a line bore of all main bearing housings. There are two principal reasons:
- To ensure that the effects of any movement of the cylinder block as a result of repairs and general age are removed
- To allow the use of modern lip seals and particularly for the rear crankcase seal to ensure a good oil tight fit.
- Cylinder head – rework, defect rectification, unleaded conversion – purpose. Engines that have done extensive miles in service, especially when oil changes have not been as frequent as they should, often suffer from worn valve guides. Wear here need not cause a reduction in performance, but oil consumption and contamination will significantly increase. Over time, this will have wider consequences. Other common faults include burnt valves, caused by poor seating and effects of foreign object damage, caused by loose nuts and washers finding their way into the engine from the carburettor air box, something that can happen all too easily.
Engines needing only a top overhaul can usually be safely undertaken without necessarily further need to dismantle the bottom end. It makes little economic sense while this overhaul is in progress to refrain from completing an unleaded conversion, if not already done; and while about this, it will be sensible also to replace all of the valve guides along with the new valves, seats and cam followers. The aluminium cylinder heads fitted to DB4 and later models are pretty robust and even when there are signs of cracking between spark plug boss and valve seat, it is not a major source of concern as it is easily repaired. But with the DB2/4 and in particular, the DB Mk3, this is not so. While cracked cylinder heads fitted to these models have been repaired successfully, there are many that have not. In the case of the DB Mk3, the design of the head is such that fitting hardened valve seats for an unleaded conversion is also full of risk. Fortunately it is now possible to fit an aluminium replacement head, which looks identical to the original. It also helps to reduce front-end weight, has better breathing and all round, is an improvement over the original. Camshaft bearing housings are only rarely a cause of concern, but in a full engine rebuild and certainly whenever we do unleaded conversions; we do fit new camshaft followers. We also make a point of matching ports to exhaust and inlet manifolds, which were not done when these engines were originally manufactured. There is no better way of causing significant and needless damage than when a timing chain breaks, and once worn, this can happen at any time. Whenever the head is disturbed, we will invariably fit new top and bottom timing chains.
- Alignment and balance – In any cases where there has been a need to repair liner seatings or weld any part of the cylinder block, we will always line bore all main bearing housings. We like to take particular care also to ensure that the crankshafts we fit are straight. In most cases they are but in some it is necessary to have them straightened and this is a specialist job. It is always good practice and a standard feature on our engine rebuilds to ensure that all of the dynamic components are fully balanced. Our first objective is to ensure that all pistons and then all con rods are weight matched to a tolerance not exceeding 0.6 gram. We statically and then dynamically balance the crankshaft. We then fit the flywheel and clutch to the crankshaft and statically and dynamically balance the complete assembly and repeat again for the addition of the vibration damper on the front end..
- Assembly – There are many joints, fine tolerances to achieve and not a little know how to be able to assemble an Aston Martin engine and get it performing, as we know it can. It requires painstaking attention to detail, scrupulously clean assembly and time to achieve, which is why a good rebuild costs the money it does. A mark of a good engine rebuild is one that it is oil tight and the oil pressure is fully up to the mark required. A finely balanced engine will always be smooth and free revving, and any that are not need to be checked out carefully to find the reason.
- Finish – There is a particular pleasure in opening the bonnet to uncover a gleaming and beautifully finished engine. We nickel plate and polish a significant number of components to achieve that as new finish, but the time and effort in doing so is never wasted. We always rebuild our engines with new studs, washers and nuts and where appropriate stainless locking wire.
- Running in and test – Any engine that is removed from a car for work will usually be put on the dynamometer prior to refitting in the car. This is to ensure that the engine is fully performing, but it also affords the opportunity to run-in a rebuilt engine under carefully controlled variable load and speed conditions. Using a fully instrumented facility also gives the perfect environment to achieve the optimal tune and timing for the engine. Final adjustments are undertaken with the engine in the car but any such adjustments are usually small with few if any defects requiring rectification.
- ZF Gearboxes - ZF Gearboxes are pretty robust or to coin a phrase, “bomb proof”. But they are now old and seen in most cases heavy use with often minimal maintenance; and they do wear and become noisy and difficult to use. They can be reconditioned, but the required components are sometimes difficult to source.
- David Brown Gearboxes – These are fitted to early DB4 and all of the DB2 and 2/4 models built during the 1950s. Their primary weakness is with the First and Reverse Gears, which wear and are damaged because syncromesh is only on 2nd, 3rd and 4th gears. The Syncromesh cones wear and occasionally tip, thereby preventing gear selection. It is now possible to replace with new all of the normal wearing components but the parts required can be difficult to source. From time to time requests are made to convert a DB Gearbox to take an overdrive and thereby provide a 5th gear. While sourcing an appropriate overdrive may be possible the other components are unfortunately no longer available.
- Manual versus automatic –the vast majority of Aston Martins manufactured up until the end of the 1960’s were manual cars with the proportion of DB6 cars having automatics around 20%, with the proportion of V8 cars made in the 1970’s and onwards being 80% autos and the others manuals. Today, we find well over 80% of cars in the executive and luxury class are autos. An increasing number of our customers have little experience of the use of manual gearboxes and in today’s traffic conditions, would prefer an auto in any case.
DB6 Astons were fitted with the Borg Warner type 35 gearbox which continued with the DBS and early V8s. Robust and long lived though they are, by today’s standards they are power sapping, with slow changes and having only 3 speeds and a lower final drive ratio, make the cars fussy and significantly thirstier on the auto routes. They detract from the character of the car and hence find little favour with the purists. However, we can now fit a modern electronically controlled 4 speed auto that behaves much as a modern. They mitigate the shortcomings and help enormously to enhance the practicality and pleasure of driving these cars in congested traffic.
Should you, however, want a manual gearbox, other options are also available. We have a few ZF manual 5 speed gearboxes. ZF gearboxes we can recondition. Alternatively we can use a modern manual gearbox with a feel closer to today’s cars. Either Borg Warner or Toyota gearboxes for example have been fitted. As always, the more extensive departure from the standard specification, the more costly the adaptation, but nothing need be ruled out.
- Importance of originality versus usability – As mentioned above, increasingly our customers want automatics, particularly with respect to models of the 1980’s and later. But we also find an increasing trend to specify an auto option on restoring early DB4, DB5 and DB6s. Whereas five or more years ago, an auto was always less valuable than a manual, this price differential has all but gone. Today having a modern non-original gearbox is no barrier to a good sale price and is unlikely to affect its value against an original manual car. The choice is for you the customer. Today practicality and ease of use are at least as important as originality. If originality is essential, we can always ensure that the original gearbox can be retained, thus facilitating the return of your car to its original manufacturers specification as and when you wish to sell her on, though few of our customers are particularly concerned.
- Improving drivability – We have a substantial reversal of usage in todays driving compared to when our DB4 or DB5 was made in the 1960’s. Then, most driving was on single carriageway two way roads where acceleration was more important than high speed cruising. We now find that driving on two way roads is much more speed constrained, with much long distance driving predominantly on dual carriageways multilane auto routes. Therefore we need to place a premium on the ability to maintain high cruising speeds (for long periods without undue noise, fussiness and good economy. The simplest option to reduce the final drive ratio to increase the cruising speed potential at lower rpm. Even a 5% change can make a difference and with little practical reduction in acceleration. A 20% change would have a noticeable effect on acceleration, but somewhere between the two a good compromise is possible. Fuel consumption would be typically reduced by a comparable amount under cruising conditions. For those with cars fitted with the original 3 speed auto, a modern 4 speed auto alternative will make a huge difference.
- Opportunity for modification – the ideal time to modify your car with an alternative gearbox and /or final drive ratio is during a restoration when everything is out of the car, and any required structural and mechanical adaptations can be implemented easily. However, such modifications can be accommodated at any time.
- Overhaul on condition – Gearboxes and Final Drives are almost always reconditioned items. The extent of a recondition depends on its pre recondition state, but it is normal practice for a full gear box recondition to:
- Complete strip and examination
- Bead blast casing
- Check Main, Drive, Lay shafts and Reverse Gear Pinions for wear or surface damage
- Check gears for evidence of damage or wear, replacing if necessary with alternative gears if required
- Internal surface coat the casing interior to reduce potential sources of oil contamination
- Replace all bearings and thrust washers
- Replace syncromesh cones
- Reassemble with all new seals and other components as required.
- Preparation – Thorough preparation is the key to any good paint finish, which marks out the key difference between the budget and the quality finish. Not only is it essential to remove any vestiges of corrosion, but the surface must be sound, properly primed and perfectly smooth. We have already mentioned the importance of shape and getting the gapping right during panel preparation; but it is such an important contributor to the final finish that it deserves mentioning again. There are usually two priming stages, depending on whether bare metal or old paint is being recoated. The first over bare metal consists of an etch primer. Its key role is to provide the best possible adhesion for the subsequent coats to the underlying metal and is first stage of the anti corrosion protection. The primer that follows is usually put on fairly thickly. This provides a partially sacrificial surface for the final “wet and dry” to achieve the perfectly smooth surface for the colour and subsequent clear lacquer coats.
- Cleanliness - Cleanliness is everything. If the paint surface is to be durable then a complete freedom from any surface contaminates is essential. Contaminates too often present range from moisture, through silicone (which is hard to shift), grease, dust and stray traces of non compatible paints previously used. These all have to be removed.
- Modern paints and what is permitted by Environmental and Health and Safety Law – Since this year, no more of the Acrylic, Cellulose or Iso-Cyanate based paints can be manufactured. Aston Workshop therefore now exclusively uses water based colour coats and lacquers. However, to use these types of paint successfully requires an up to date spray booth which we have.
- Matching colours – Matching existing paint work used to be an art. Today, technology helps in the form of an optical “tablet”. Used widely at the Prestige end of the industry, it provides a consistent close match. Computer based, this then provides a precise specification for the colour mix, leaving the final close colour match for the painter to very slightly adjust to achieve the optimum result.