This car, in the modifications undergone since its building in 1958, brings to light some of the complex history of the engines in AC cars of this era. This is chassis AE 708, first registered on 24 December 1958 with the classic 1991cc six-cylinder AC engine. The car was fitted in the early 1960s with a Ruddspeed Ford Zephyr 213E engine, a Moss gearbox with overdrive on 3rd and 4th gears, disc brakes and an uprated Piper camshaft.
These two engines were used in the Aceca and its sister models, the convertible and the Greyhound coupé, along with perhaps the most famous powerplant, the 6-cylinder 2-litre Bristol engine. However, the chassis number of this car confirms its original AC engine: in Ace and Aceca models AE denotes such an engine, whereas a genuine Ford-engined AC would have the chassis number RS for Ruddspeed.
The original AC engine dates to 1919. Designed by John Weller, it was advanced for its time. The straight-six featured a lightweight aluminium alloy crankcase/water-jacket and sump, cast iron cross-flow head and single overhead camshaft. Initially the camshaft was driven via a vertical driveshaft and skew gears, but this was quickly replaced by an inverted tooth chain (later replaced by a duplex chain drive) with Weller’s own patented tensioner (a simple spring-steel strip). It had wet cylinder-liners and a four-bearing crankshaft (a fifth bearing was subsequently added to the rear).
Auxiliary drives were also well designed. The camshaft, distributor and dynamo all took their drives from the rear of the crankshaft, avoiding the torsional vibration emanating from the crankshaft when the drive is taken from the front of the engine. This provided a smoother drive with more consistent cam timing.
However, by the postwar period the venerable AC engine was beginning to be outdated. The initial solution was to use the BMW-derived six-cylinder Bristol engine, but supplies of the engine were diminishing as Bristol converted to Chrysler V8 power in 1961, and Ken Rudd proposed the 2.6-litre Ford Zephyr engine, suitably tuned. The effect on power was remarkable. The AC unit produced only 100 bhp, whereas the Ruddspeed unit put out a healthy 170 bhp. It is not surprising that the owner of this car, seeing what AC had done, made the conversion.
Both Ace and Aceca had advanced underpinnings, with all-round independent suspension using transverse leaf springs. The convertible AC Ace may have been the most exciting of the two models, but the closed Aceca was only slightly heavier than the Ace, and because of better aerodynamics was also slightly faster. So, far from being the poor relation of the Ace, this Aceca with a Ruddspeed Ford engine is a fine example of the marque.
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