Everyone knows that the legendary Shelby Cobra was of course an AC Ace with a massive dose of Ford V8 hormones. But probably fewer of us know much about the actual Ace, before that intervention by Carroll Shelby. This vintage SCI test was the first time I’d read anything of the kind, a comprehensive review of the Ace as it was in 1957 with its 2 L OHC inline AC six that dated all the way to back to 1919. Hard to believe, actually, given how much progress there was in engine design in the 40 some years it was in contiguous use.
It should be noted that as of 1956, the Ace was also available with a more potent Bristol 2 L six, a design based on the prewar BMW 328, but only some 20 years old instead of 40. And in 1961, there was also a version with a modified 2.6 L Ford Zephyr six. The Ace was an excellent chassis with a svelte bod apparently always on the lookout for a new engine. It found that soon enough.
I’m not going to do a full history of AC Cars, which dates back to 1901. But the key thread that leads to the Ace started in 1919-1920, with the AC 12 HP Tourer (above) and its superb new OHC six cylinder engine designed by John Weller, one of the two founding brothers. It was highly advanced for the times. It initially displaced 1447cc and made 40hp. In May 1924, at Montlhéry near Paris, T.G. Gillett broke the continuous 24-hour record in a 2-litre AC with special bodywork.
The Wellers lost control of the company during the Depression, but AC survived. Given the intrinsic sporting capabilities of the six, AC developed a line of sporting cars to maximize its potential, such as this beautiful one from 1937.
After the war, AC built the Two Liter as a sporty tourer, in both convertible and saloon body styles from 1947 to 1956.
The company desperately needed a new chassis and body to compete in the sports car boom of the 1950s, and found it in this roadster designed by John Tojeiro. The chassis was based on two main tubular frame members and independent suspension front and rear via upper transverse leaf springs and lower control arms. For 1953, it was quite advanced, especially the rear suspension. The lightweight aluminum body is undoubtedly inspired by the Ferrari Barchetta of 1949.
Here’s a better view of that 1919 engine, which used three SU carbs from day one. It has an aluminum block with wet cylinder liners and a cast iron hemi-head cylinder head. It really didn’t change very much at all in the ensuing decades, except that its performance steadily increased from 40 to some 100 hp. The 1957 version tested here was rated at 90 hp @4500 rpm. It was a classic undersquare British engine, with a 2.56″ bore and a massive 3.94″ stroke.
That may not sound like much, but it could keep up with a new Thunderbird V8 in acceleration up to 75 mph.
Acceleration (0-60 in 11.6 sec.) might seem a bit modest from our current POV but in 1957 this was right in the ball game with most of the better/quicker sports car, as we’ll see from upcoming reviews from this issue. Acceleration isn’t everything.
The Ace’s handling, steering and brakes were stellar, including on rough surfaces. This is what set it apart from the more primitive competition from Austin-Healey, Jaguar, and the like, including the Corvette. All suffered from their more primitive underpinnings, especially their leaf sprung solid rear axles.
Those dashpot carbs symbolize Britain even more than RHD steering.
Always loved these, but you rarely saw them on the road, even though they were popular on the race track.
That A C motor was still pretty advanced in 1953, only the long stroke betrayed its’ age. I’m not sure about it having a four-valve head though – the illustration of the rockers suggests only twelve in total. The magazine test in ’57 also shows rack and pinion steering, but I think the early cars were more primitive.
The Bristol motor added a big chunk to the purchase price but kept the car competitive on track. The 2.6 litre Ford motor was only used after supplies of Bristol motors ended, but the Ford-engined cars introduced the longer snout that carried over to the Cobras.
I assumed it was a two valve motor but then one of the articles I was reading for source material said it had four. But obviously it doesn’t.
The performance seems really impressive for such an early engine design. Even the fuel economy is strong for a car with 90 horsepower in the fifties, although I suppose part of that is light weight. I always thought it was entertaining how the AC sports cars went from a 1919 engine with overhead cam and a crossflow head to a 1939 engine with dual rocker shafts operated by pushrods giving a crossflow configuration to a 1950s engine and then an early ’60s engine designed with pushrods and inline canted valves.
I saw this beautifully ragged Ace-Bristol at the antique races back in 2008. Needless to say, it drew a lot of attention that day.
How fascinating to read a test of the Ace with the original AC-designed engine!
I’m intrigued by the drive chain for the overhead cam coming off the flywheel end of the engine; that must’ve made changing the drive chain fun!
It’s interesting to see the engine originally displaced 1447cc. What was it with the British and their fascination with tiny sixes through the twenties and early thirties? I don’t think the RAC hp tax system gave any advantage to a six over a similarly-sized four. I can see that a small six would be smooth to drive, but surely they would be rather torqueless affairs like the small Japanese V6s of the nineties, and with the long-stroke design you couldn’t rely on revs. Obviously with the AC it wasn’t a case of adding two cylinders to an existing engine, like some later proponents seemed to do.
The more I look into the AC’s design, the more I realize how amazing it was for its time.
In their early 1960s test of the Triumph Vitesse, Road & Track said there was a time when cars didn’t have vibration-absorbing rubber engine mounts, and a lot of engine vibration was transmitted into the chassis. Hence the thing for light sixes, as they were called.
Out of curiosity I went on NADAguides.com and checked the original 1957 prices of the Ace and a couple of comparable roadsters.
Jaguar XK140M: $3595
Mercedes 190SL: $4652
AC Ace: $4550
I assume that in 1957 that wasn’t cheap, and the $1000 difference between the Jaguar and the AC was non-trivial.
Where’s page 128? 🙂
Oops! It’s there now. 🙂
I wonder who Eric George Gray was, as it seems it was he who designed the sexy clothes for that sexy chassis? It’s a delicately beautiful car, which something not obvious in the Cobra, where it seems Ace’s swallowing of a huge American made it bulge in a quite unseemly manner.
In ’57, I’m pretty sure a Ferrari didn’t have tubular shocks, and certainly no proper rear end with decent geometry. And 11 inch finned alloy brakes to stop just 1900 lbs, and rack and pinion, and front-mid engined to boot. Very nice indeed.
Interesting that the weight distribution is so rear-biased: means that that sophisticated rear end is thoroughly necessary, I guess, and despite Ac’s claim, it does look like a set-up for racing. Driving about pivoting off the rear sounds a bit advanced for road use, though in the 60mph photo, the suspension positions look modern (ie: no positive camber, folding under outside front, or poorly angled inside rear).
The old engine is a good-looker. Just look at the art in that fan carrier alone, which is apparently not really needed anyway, it seems. Very impressive urge for just 2 litres with a 4,500 rpm limit.
All pleasurable in dry weather, mind. Only in rainy England could a motorcar be made with an inherently leaky roof.
(Just realised why one gets such an uncluttered, un-self-indulgent yet characterful sense of the car: it’s Griff Borgeson writing1)
Griff Borgeson was a straight shooter.
Interesting the AC had an alloy block and cast iron head and was in production for decades. GM’s efforts with same were not quite so long-lived.
I didn’t say it had a cast iron head. It’s aluminum too. As well as the sump and pistons.
Aluminum blocks and heads were actually fairly common back in the early decades of the car. They obviously used a cast iron cylinder liner.
The head is cast iron.
I stand corrected.
But there’s no intrinsic reason that an iron head on an aluminum block should be an issue. The Vega’s engine’s issues were not for that specific reason per se.
Even with the more rational pairing of an iron block and an aluminum head, many car companies were struggling with getting head-gaskets to seal with the differential in expansion rates of the dissimilar metals. When the AC engine was designed, many high performance overhead valve engines didn’t even have removable heads because head-gasket technology wasn’t up to the task even if everything was the same metal.
This car had an 8:1 compression ratio, which I’m sure was a point and a half higher than it was originally designed for because fuels improved over that thirty-eight year period. I wouldn’t be surprised to learn that anything approaching overheating meant decking the block and replacing the head-gasket.
I doubt this engine had a head gasket resembling a modern head gasket. Most likely it had a separate copper ring for each individual cylinder and separate little fiber gaskets for the oil and water ports.
I remember Dad’s old MO-series Morris Oxford (think Minor blown up to 130%) cracked the sump in a creek crossing in outback Queensland once. He was shocked to find that old-style sidevalve motor had a cast alloy sump. Postwar British steel shortage I guess.
There was also a coupe version, the Aceca. Apparently the AC 2 Litre was an interesting car in its own right:
http://www.ac2litre.com/index.html