Guide: Aston Martin DB4 GT - a Historical & Technical Appraisal
Background
1954’s Appendix J regulations added a new Grand Touring class to motor racing’s existing regularity framework. Qualification required a manufacturer build at least 100 base cars during a twelve month period to which certain adaptions such as tuned engines, special coachwork and modified chassis were then permitted for competition use.
To attract more participants, many race organisers began to introduce separate classes for GT cars during the years that followed. However, for the time being, most manufacturers remained focused on purpose-built sports prototypes for their factory racing efforts although firms like Ferrari began to do a roaring trade selling independent teams and gentleman drivers Competizione versions of their Gran Turismo models.
Since late 1951, David Brown’s works Aston Martin equipe had gone racing with tailor-made ultra specialised racing models like the DB3, DB3S, DBR1 and DBR2.
Between 1952 and 1958, the team won a series of major races every year. The programme culminated with Aston Martin being crowned 1959 World Sportscar Champions following wins for the DBR1 at that year’s Nurburgring 1000km, Le Mans 24 Hours and Goodwood Tourist Trophy.
In addition to having been notable for the success of Roy Salvadori and Carroll Shelby in a DBR1, the 1959 Le Mans 24 Hours was also significant as it was the first year that the Automobile Club de l’Ouest had organised a Grand Touring class for which Aston Martin entered a prototype DB4-based machine dubbed the DP199.
Based on a shortened DB4 chassis fitted with a tuned engine and a host of lightweight equipment to include a reworked air-piercing body, the DP199 (with which Stirling Moss had won the Silverstone International Trophy in early May) ultimately retired during the third hour when its engine ran a bearing.
Afterwards, the DP199 returned to Newport Pagnell where it served as a development mule for a racey new production model: the DB4 GT.
Unveiled twelve months after the original DB4 at the London Motor Show in October 1959 (where a freshened up DP199 was actually presented), the DB4 GT was conceived as an ultra high performance iteration of the regular DB4 that could, if suitably configured, race at the top international level.
Alternatively, customers that simply wanted to take possession of the fastest Aston Martin road car ever offered could order their DB4 GT in standard trim with a full array of comfort equipment.
As for those handful of customers that did want to compete, they would have more opportunities than ever before particularly as, for 1960, the Federation Internationale de l’Automobile were set to organise the inaugural FIA GT Cup, a five race series for Grand Touring cars that comprised the Sebring 12 Hours (March 26th), the Nurburgring 1000km (May 22nd), the Le Mans 24 Hours (June 25th and 26th), the Goodwood Tourist Trophy (August 20th) and the Monza Coppa Inter-Europa (September 4th).
The races at Sebring, the Nurburgring and Le Mans also served as rounds two, four and five of that year’s World Sportscar Championship while the Goodwood and Monza events were stand-alone FIA GT contests.
Chassis
Like the DP199, the DB4 GT was based around a shortened version of the regular DB4’s pressed steel monocoque. At 2363mm, 127mm (or five-inches) had been cut from the wheelbase in order to reduce weight, increase rigidity and improve handling.
Although plans for a de Dion rear axle had been discussed, Aston Martin elected to retain the standard DB4 suspension layout. This comprised a double wishbone configuration up front along with coil sprung dampers and an anti-roll bar. At the back was a live rear axle with parallel trailing links, coil sprung dampers and a Watt’s linkage.
Disc brakes were fitted on both axles (as per the DB4 which had been the first Aston Martin road car thus equipped), but for the GT larger diameter Girling as opposed to Dunlop discs were used and the servo-assistance was ditched to reduce weight and improve feel.
More weight was cut thanks to lighter 16-inch Borrani wire wheels which now came with three instead of two-eared spinners.
For increased range, the standard 19 gallon fuel tank was replaced by a light alloy 30 gallon unit. The spare wheel was mounted on top which meant luggage space in the trunk was greatly reduced.
Engine / Gearbox
In addition to a monocoque chassis and four-wheel disc brakes, another of the DB4’s significant updates had been its thoroughly reworked iteration of Aston Martin’s existing dual overhead cam straight six.
Redesigned by Polish engineer Tadek Marek, the DB4 engine most notably featured an alloy instead of cast-iron block (saving 22kg) along with substantially increased displacement (from 2922cc to 3670cc).
For the GT variant, Aston Martin retained the existing 92mm bore and stroke along with a wet-sump lubrication system, but added a whole bunch of new performance-optimising equipment.
For starters, the block and head were now fashioned from lighter than normal RR50 alloy.
The GT-specific head featured high-lift camshafts and twin instead of single plug ignition fed by two distributors as opposed to one. The modified head also allowed the compression ratio to be increased (from 8.25:1 to 9.0:1).
A bank of three sidedraught Weber 45 DCOE carburettors with cold air collection box replaced the twin SU HD8 items normally fitted.
All told, peak output was now 302bhp at 6000rpm and 270lb-ft at 5000rpm.
For comparison, the standard DB4 pumped out 240bhp at 5000rpm and 240lb-ft at 4200rpm.
Transmission was through a close-ratio version of the existing David Brown four-speed gearbox, a 9-inch twin-plate rather than 10-inch single-plate clutch and a Salisbury Powr-Lock limited-slip differential which was fitted as standard.
Bodywork
DB4 GT bodywork was much the same as pioneered by the DP199.
Instead of the regular DB4’s exposed headlights, GT versions featured an aerodynamically-profiled nose with more pronounced pontoon-style enders and a pair of faired-in headlights mounted behind contoured Plexiglas covers.
Much shorter doors were fitted as dictated by the reduced wheelbase.
Like early DB4s, the doors did not come with window frames.
Instead of a single fuel filler cap concealed behind a flap on the left-hand sail panel, the GT was equipped with a pair of exposed quick fuel filler caps sunk into the tops of the rear fenders.
To save weight, body panels were fashioned from 18 gauge (1.2mm) magnesium alloy. In addition, the rear quarter windows and rear windscreen were switched to Plexiglas and overrider-less bumpers were used.
Initially, four slim intakes were carved out from the front apron, the outer pair of which fed fresh air to the brakes with the inner pair ducted to the oil cooler.
With its state-of-art aerodynamically profiled nose, handsome proportions and Fastback tail with discrete rear fins, the DB4 GT was arguably the most stylish Grand Tourer of its day. Cutting edge features were combined with elegant details throughout to create a rakish machine that was a significant evolution of the Touring of Milan-styled original.
Owing to the DB4’s steel monocoque-type construction, Touring’s famed Superleggera construction technique was only required for the bonnet surround, windscreen, roof, rear wings and tail. The bodies themselves were manufactured under licence at Aston Martin’s Newport Pagnell factory.
Interior
Instead of the standard four-gauge plus clock dash layout of the standard DB4, the GT adopted a seven-gauge plus clock arrangement.
A large 7000rpm rev counter and 180mph / 300kmh speedometer replaced the original 6000rpm and 160mph / 240kmh items usually fitted. Mounted in between them was a small ammeter.
Outboard of these, the combined ammeter / water temperature and oil pressure / fuel dials were replaced with four smaller individual gauges (water temperature, fuel level, oil pressure and a new oil temperature read out that was exclusive to the GT).
As usual, the instrumentation was mounted on a semi gloss black dash imported from the regular DB4, the forward upper section of which was trimmed in black leatherette. A wood-rimmed steering wheel complete with David Brown insignia was given three semi gloss spokes to match the dash.
Aside from its new instrumentation, the GT most obviously differed from the regular DB4 on account of its re-modelled rear quarters which saw the back seats deleted in favour of a carpeted luggage platform. In addition to its weight reduction properties, the newly configured rear quarters were essential as the GT’s long-range fuel tank had swallowed up most of the trunk’s storage capacity.
Otherwise, the GT was finished to the same very high specification as any other DB4 with a properly trimmed leather and carpeted interior that was light, airy and offered excellent all-round visibility.
Options
In addition to a wide range of exterior and interior colour combinations, GT buyers could opt to have their car equipped with extras such as a radio, a pair of small rear seats, servo-assisted brakes and a standard fuel tank.
Lightweight Version
Aston Martin also offered a special Lightweight version designed for racing use.
In terms of specification, Lightweight cars varied from one example to the next, however, the full package of modifications included a drilled monocoque, aluminium instead of steel for much of the floor and bulkheads, a blueprinted engine, fabric bucket seats, more basic upholstery with thin vinyl and rubber matting replacing much of the original leather and carpet, Plexiglas side windows, simplified door panels, no glovebox lid and drilled pedals (clutch and brake).
Weight / Performance
In conventional trim, the DB4 GT had a kerb weight of 85kg less than a regular DB4 (1269kg as opposed to 1354kg).
Top speed went from 140mph to 153mph and the 0-62mph time dropped from 7.2 to 6.1 seconds.
In Lightweight specification these cars were even faster. With another 141kg cut from the kerb weight (taking them to 1128kg), they were capable of hitting 62mph from a standstill in around 5.3 seconds and a top speed in excess of 155mph.
Early Production Changes
The first 23 DB4s built to GT trim used the aforementioned front apron set-up with four slim intakes (outboard for brakes, inboard for the oil cooler). However, this was subsequently switched to a DP199 set-up with one much larger now centrally located duct for the oil cooler.
In some cars, the cylinder bores were enlarged by 1mm for a displacement of 3750cc.
During April 1960, Aston Martin switched all DB4 GT engine numbers to a four digit system fronted by a zero.
DB4 GT Zagato
One year after having launched the DB4 GT, Aston Martin unveiled a Zagato-bodied variant with a further uprated 314bhp engine (covered separately).
The DB4 GT Zagato (also dubbed the GTZ) was unveiled at the London Motor Show in October 1960 and effectively replaced the standard DB4 GT for the 1961 season.
DB4 GT Bertone Jet
At the Geneva Motor Show in March 1961, Bertone unveiled a one-off DB4 GT dubbed the Jet with completely new coachwork and interior (covered separately).
Later Production Changes
From spring 1961 (following the introduction of the Series 3 DB4 that April), some cars began to come with three circular tail lights per side mounted inside a chrome shroud to replace the original clusters which had been sourced from the DB Mk3.
Similarly, from autumn 1961 (following the introduction of the Series 4 DB4 that September), the original meshed front grille was switched to a bar-type grille.
End of Production
DB4 GT production was discontinued in June 1963 by which time 75 examples had been built. Of these, 45 were right-hand drive and 30 were left-hand drive. Chassis numbers ranged from DB4GT/0101/L to DB4GT/0175/L.
Between four and nine cars were built to Lightweight trim. The number varies according to precisely what level of specification constitutes a true Lightweight. Aston Martin themselves consider eight cars to have been built to Lightweight trim.
Continuation Cars
In February 2017, Aston Martin announced they would construct a batch of 25 track-only continuation cars to DB4 GT Lightweight specification.
Production took place at the Newport Pagnell factory where the original variants had been built during the 1960s. The last new car to have rolled out of this facility had been a V12 Vanquish S ten years prior.
In contrast to the original Lightweight, these continuation cars (which were priced at £1.5m apiece) came with a modern FIA-grade rollcage, seats and fuel tank, rose-jointed suspension and a 4.2-litre 340bhp engine hooked up to a non-synchromesh four-speed ‘box with straight-cut gears. Weight was 1260kg.
Competition History
Following the exploits of the DP199 (in which Stirling Moss won a race for Production GT cars at the 1959 Silverstone International Trophy and Hubert Patthey / Renaud Calderari posted a DNF at the Le Mans 24 Hours), the first event for a DB4 GT proper was at the end-of-season Bahamas Speed Weeks where Moss drove Frank de Arellano’s example (chassis 0103/L) to victory in the Nassau Tourist Trophy Preliminary. Unfortunately, a bent valve in the main event while leading caused 0103/L to retire and precluded Arellano from taking the wheel in the subsequent Nassau Trophy race.
During the 1960 season, Tommy Sopwith’s Equipe Endeavour and John Ogier’s Essex Racing Stable ran the DB4 GT with factory assistance. After a superb 1959 campaign that had seen the DBR1 finish first and second at Le Mans and Aston Martin claim that year’s World Sportscar Championship, David Brown had decided to quit sportscar racing to focus on Formula 1.
Meanwhile, at domestic level the DB4 GT proved difficult to beat.
Driving Tommy Sopwith’s car (chassis 0124/R), Stilring Moss won the Fordwater Trophy at Goodwood while Jack Sears won races at Aintree, Oulton Park, Snetterton and Brands Hatch, routinely setting new lap records along the way.
The brace of Essex Racing Stable machines (0125/R and 0151/R) ventured a little further afield once the first car had been delivered mid-season. Most notably, Roy Salvadori (0125/R) and Innes Ireland (0151/R) finished second and third in the Goodwood Tourist Trophy (round four of the FIA GT Cup) and would have been in contention for victory were it not for the team’s slower tyre changes.
At the season-ending Paris 1000km around Montlhery, Jim Clark and Tony Maggs looked set for a strong finish in 0151/R until its engine dropped a cylinder while the badly blowing 0125/R driven by Ireland and Salvadori wheezed its way to sixth.
A number of good results were also achieved heading into 1961, but by this time the Zagato-bodied version was beginning to appear on the scene and Ferrari’s continually uprated 250 GT SWB Berlinetta had established itself as the dominant GT racing car.
Text copyright: Supercar Nostalgia
Photo copyright: Aston Martin - https://www.astonmartin.com & RM Sotheby’s - https://rmsothebys.com/
