Guide: Cobra Progenitor - a Historical & Technical Appraisal of the AC Ace & Aceca
BACKGROUND
During World War 2, AC’s Thames-Ditton factory had produced Swordfish and Albacore components for Fairey Aviation along with Ordnance QF 6-pounder anti-tank guns, glider undercarriages, flame throwers, fire pump trailers and bodies for Bedford and Ford fire engines.
Unlike the build up to hostilities, which had generally seen patchy sales and stop-start production as the company passed through the hands of various different owners, World War 2 proved very profitable for AC and the company emerged in good financial health.
Car production re-started in late 1947 with a two-door Saloon dubbed the AC 2-litre which used a wood-framed aluminium body mounted to a conventional tubular steel chassis with leaf sprung suspension. In the engine bay was an updated version of the company’s two-litre single overhead cam alloy-block straight six which developed a respectable 74bhp.
The following year (1948), AC secured a substantial ongoing contract with the British government to produce the 197cc Villiers-powered Invacar, a single seat three-wheeled invalid carriage that was supplied free-of-charge to disabled people and which continued to prove a steady source of income for more than two decades.
By the early 1950s, AC’s 2-litre model was really beginning t show its age and company management began to explore the possibility of creating an exciting new model that could take the firm into the 1960s.
What emerged was a two-seat Roadster dubbed the Ace based on a chassis designed by upcoming freelance engineer, John Tojeiro.
1953 had seen a small batch of Tojeiro-designed racing cars impress at circuits around the UK, one having been powered by a two-litre six cylinder Bristol engine (owned by Cliff Allison) and the other a 2.5-litre Lea Francis motor (owned by Vincent Davison). They were draped in elegant fully enveloped aluminium bodies and caught the attention of AC’s owner, Charles Hurlock.
Following a demonstration of the Lea Francis-powered car, this particular Tojeiro was purchased by AC to serve as the basis for their new production offering. Motor engineer Davison was brought on board to serve as a development engineer along with John Tojeiro who was tasked with overseeing the new design. During the late summer of 1953, the Tojeiro-based Ace Prototype (registered TPL 792) was fitted with AC’s latest 2-litre engine and refined into something a little more civilised.
In its freshened up form, TPL 792 was presented alongside a naked version of the first true Ace chassis (number AE 01) at the October 1953 London Motor Show.
By the time production began in May 1954, the Ace had been equipped with a gorgeous new body and transformed into a spectacular fully equipped machine suitable for either road or competition use.
CHASSIS
The Ace’s John Tojeiro-designed ladder-type steel chassis was based around two large diameter tubes with front and rear subframes to which the suspension was attached. A skeletal frame of smaller diameter steel tubes was used to support the aluminium body. The wheelbase measured 2286mm (90-inches).
With coil sprung dampers running off a transverse leaf spring at either end, AC proclaimed the Ace to be the first post-war British sports car that offered all-round independent suspension.
Steering was through a Bishop Cam screw and follower arrangement.
A 12 UK gallon fuel tank (14.4 US gallons or 54.5-litres) was mounted under the trunk floor.
The braking system comprised a Girling hydraulic circuit with 11-inch diameter Wellworthy Alfin drums at either end.
Centre-laced 16-inch diameter wire wheels (painted silver, cream or red) were originally shod with 5.50 R 16 Michelin X tyres.
ENGINE / TRANSMISSION
In the engine bay was AC’s latest iteration of its Light Six engine, the origins of which could be traced back to 1919 when John Weller designed it under the direction of shareholder Selwyn Francis Edge who ultimately took control of the company in 1922.
The single overhead camshaft straight six featured an aluminium alloy block with cast-iron head and displaced 1991cc thanks to a bore and stroke of 65mm x 100mm.
For this latest application, the UMB / UMC line of engines featured a repositioned water pump, vibration damper and harmonic balancer while bronze-backed white-metalled bearings replaced die-cast white metal and new engine mounts were adopted.
With a compression ratio of 8.0:1 and three SU H2 1.25-inch sidedraught carburettors, peak output was 85bhp at 4500rpm and 110lb-ft at 2500rpm.
The entire electrical system (dynamo, coil, distributor, horns, wiper motor, battery and lights) came from Lucas.
Transmission was through a Moss four-speed gearbox, single-plate Borg & Beck clutch, Hardy Spicer final drive and open differential.
BODYWORK
Styling-wise, the Ace body was an in-house collaboration between Alan Turner and Eric George Gray.
At the front it followed conventional design practice for the time with a large primary nose intake, exposed headlights and a gently rounded fenders that swept back towards the cockpit.
Weather protection for the cabin comprised a full-width detachable windscreen, similarly detachable two-piece sidescreens and a basic canvas roof with framework that had to be manually assembled and dis-assembled each time. A full cockpit tonneau cover was supplied too.
Access to the cabin was by way of small doors without any exterior handles.
Behind the doors, pronounced kick-up rear fenders flowed back towards the closely cropped tail. Located on the left-hand rear fender was an exposed quick fuel filler cap.
Vertical overriders were fitted at either end, one type of which was able to accommodate the optional full width bumpers.
The Ace’s aluminium body panels were fashioned on a wheeling machine and then welded together before final shaping took place on wooden bucks. Once a satisfactory profile was achieved, the panels were pop riveted in place.
INTERIOR
Inside, the Ace was equipped with a fully trimmed cockpit that included everything needed for road use.
Standard issue was a Bluemels bakelite steering wheel which featured three groups of four banjo spokes that connected the rim to the boss.
The aluminium dash was covered in leather colour matched to the rest of the upholstery. Positioned on either side of the height-adjustable steering column was large speedometer (complete with with inset clock) and a matching rev counter. Four smaller read outs (water temperature, oil pressure and fuel along with an ammeter located underneath) were housed towards the centre of the dash.
Single-piece leather bucket seats were trimmed with pleated faces and carpeted backs. They could be adjusted fore / aft only. The doors, sidewalls and rear bulkhead were upholstered in a mixture of leather and carpet.
Leather door opening straps were fitted as opposed to conventional release catches.
Lovely AC-branded cast aluminium pedals were fitted to each car.
OPTIONS
AC offered a comprehensive list of optional extras for the Ace to include chrome-plated wheels or wheels painted a colour other than silver, cream or red, a fibreglass hardtop, racing-style aero screens, full width front and rear bumpers, windscreen washers, external boot hinges, a wood-rimmed steering wheel, a heater, a windscreen demister, a radio and an oil temperature gauge.
Other upgrades comprised a Moss SH gearbox with more rearward gear lever (and which could be ordered with closer ratios), a choice of alternative rear axle ratios, a second ignition coil, a secondary petrol pump, an oil cooler, an aluminium instead of steel fuel tank, a supplementary fuel tank, a fuel tank shield, a second spare wheel, a battery shield and a racing cowl for the radiator.
WEIGHT / PERFORMANCE
In terms of curb weight, the Ace tipped the scales at 780kg.
Top speed was 103mph and 0-62mph took a little under ten seconds.
ACECA
At the London Motor Show in October 1954, AC debuted a fixed head Grand Touring version of the Ace dubbed the Aceca.
In line with its more refined, better equipped nature, the Aceca featured bulkheads and footwells moulded from fibreglass for improved sound insulation. The rear bulkhead was a new ‘half bulkhead’ that separated the front and rear cockpit compartments. Meshed aluminium stoneguards were fitted inside the fenders.
Although at first glance the front half of the Aceca appeared almost identical to an Ace, the upper surfaces were flatter and two banks of four louvres were carved out from the hood up near the bulkhead.
AC added a Fastback-style roof canopy that elegantly swept down towards the tail. A lift-up tailgate with perspex rear window opened to expose a good-sized luggage compartment. Wooden frames were used for the tailgate structure along with the more substantial doors which now featured proper push-button opening handles, wind-down windows and opening quarterlights. The rear side windows were hinged at their leading edge to allow for additional cockpit ventilation.
The Aceca’s sloping rear fenders were given a unique finned treatment and new lights. Housed on the tail fascia was a recessed number plate shroud with perspex cover.
Inside, AC fitted a completely redesigned dash trimmed in colour matched leather complete with new burr walnut inserts for the primary instrument binnacle, centre console panel and glovebox.
Housed in the binnacle directly behind the steering wheel was a large rev counter and speedometer (again with an integral clock. In between was a smaller read out for oil pressure. More small dials (a water temperature gauge, fuel indicator and ammeter) were located in the centre console. Above the centre console was a chromed pull-out ashtray and below it were the heater controls.
If specified, the optional radio was positioned below the glovebox.
Another unique Aceca feature was properly trimmed leather-covered door panels with window winders, opening handles, small elasticated storage pockets and burr walnut caps. Dark emerald semi-transparent sun visors were also fitted along with a cloth headliner.
Out back, the rear storage carpet was carpeted as was the ‘half bulkhead’ except for its leather top roll.
At 895kg the Aceca weighed in 115kg heavier than an Ace.
Top speed was 103mph and 0-62mph took a little over ten seconds.
AC ACE BRISTOL / ACECA BRISTOL
In 1956, AC introduced the more powerful two-litre straight six Bristol-engine as an option for the Ace and Aceca (covered separately).
AC ACE RUDDSPEED / ACECA RUDDSPEED
In 1961, AC added a second engine option: a Ruddspeed version of Ford’s 2.6-litre straight six (covered separately). However, unlike the Bristol motor (which more or less dropped straight in), these Ruddspeed variants (which were offered in myriad states of tune) required all manner of additional modification.
PRODUCTION CHANGES
Soon after production began, a strengthening web was added to the original plain tubular A-shaped front suspension wishbone, the small front indicators originally used were switched to a larger type and the original aluminium alloy front brake backing plates were changed to steel (with aluminium alloy items retained at the rear).
In 1955 (from chassis AEX 59), the original UMB / UMC series engine (which bore 2000 series numbers) was gradually phased out in favour of the CL type (with a 2100 series number). As a consequence of a larger diameter crankshaft, the CL engines produced 90bhp at an unchanged 4500rpm. The torque rating was unaffected.
A little later, the original circular tail lights were replaced with a rectangular type and the basic trunk lock was replaced with a T-handle version.
During 1956, a lid was added to the Ace’s cubby hole on the dash (which transformed it into a glovebox), a Laycock de Normanville overdrive (which operated on second, third and fourth gears) was added to the options list and (from chassis AEX 128) rubber instead of bronze bushes were adopted for all suspension pivot points.
In 1957, AC shortened the Ace’s trunk lid which enabled the trailing edge of the roof to be mounted further back. Double laced wheels were added to the options list along with 11-inch front disc brakes (the first disc brake-equipped example having been chassis BEX 289 in August 1957).
1958 saw a smaller 15-inch diameter wheel become an optional extra along with a more aerodynamic, less steeply raked curved instead of flat windscreen for the Ace that provided less buffeting. Around this time, the Aceca windscreen was given curved instead of right angled lower corners to better resist water ingress.
In 1959 (from chassis AEX 1010), AC switched to its CLB engine which featured a 9.0:1 compression ratio, higher capacity oil pump and a nitrided crankshaft with lead indium instead of bi-metal main bearings. Peak output rose to 102bhp at 5000rpm and 120lb-ft at 5000rpm.
Later that year, AC produced a lightweight gearbox option that comprised Triumph TR3 gears in a special aluminium housing with remote gearchange, a straight gear lever and a TR clutch centre plate. The first car equipped as such was chassis AE 1136.
During 1960, disc brakes and windscreen washers were made standard.
END OF PRODUCTION
223 examples of the AC-engined Ace left the factory between May 1954 and mid 1963.
151 examples of the AC-engined Aceca were completed between October 1954 and mid 1963.
COMPETITION HISTORY
Together, the Ace and Aceca went on to achieve great success in both races and rallies. A combination of impressive performance and lightweight yet rugged design meant they were well suited at both international and club level competition with both professional and amateur drivers.
Text copyright: Supercar Nostalgia
Photo copyright: AC Cars - https://ac.cars/ & Bonhams - https://www.bonhams.com/department/CAT-MOT/motoring/
