For understandable reasons, our knowledge of the historic English automaker AC Cars typically begins with something like, "Carroll Shelby happened upon AC's lightweight Ace roadster and got the idea to shove a 289 Ford V8 into it." Yet AC Cars, which is still around today and lately making electric Cobras, had been making vehicles almost continuously for 59 years before Shelby's engine bay surgery. What's more, there was a Shelby before Shelby — in this case, and English car dealer and racer named Ken Rudd, who ran a performance shop called Ruddspeed that is also still in business. The backbone of his business was improving the flyweight roadster, which included turning them into the Ruddspeed Ace. Rudd only built 37 of them, one example from 1963 is headed to the RM Sotheby's auction block during Monterey Car Week.
Rudd really did set the template for Shelby's Cobra, and he did so twice. When the Ace debuted in 1953, AC powered it with an underwhelming, 102-horsepower straight-six engine that had first seen service after World War I. Rudd, seeking more performance, sourced 2.0-liter Bristol straight-sixes with 120 hp. The Bristol mills did so well that AC switched to them for factory production. Come 1961, when Bristol couldn't supply any more engines, Rudd suggested using Ford of England's 2.6-liter straight-six doing service in the Zephyr 6 MkIII sedan that also had 120 hp. From 1961 to 1963, Ruddspeed tuned about three dozen of the Aces to get up to 170 hp with the Stage 5 package. These were the cars that Shelby took notice of. And when Shelby had an Ace flown to California in February of 1962 to be the first recipient of the small-block Ford, the sun began to set on the Ruddspeed cars.
The RM example got the Rudspeed Ace Stage 4 tune, also with 170 hp thanks to tweaks like new aluminum cylinder heads and triple SU carbs. That's 101 horsepower less than found in the 289 Cobra, but the Ruddspeed weighed 400 pounds less than the small-block Shelby. RM Sotheby's has set the pre-sale estimate at $300,000 to $375,000.
A collector that truly wishes to understand AC cars won't need to leave the RM Sotheby's tent, in fact — the auction house catalogue lists seven AC's up for sale. The history lesson starts with a 1910 AC Sociable, a three-wheeler dreamed designed at the suggestion of the company's business manager, John Portwine. He owned a chain of butcher shops in London and figured a simple delivery runabout would sell well among the commercial class. Five interwar models start with the 1928 AC 16/56 Six Royal Roadster, created when serial entrepreneur S. F. Edge ran the company, Edge having been involved in everything from bicycles to Dunlop tires to De Dion and Napier cars. The interwar period ends with the 1938 AC 16/90 Two-Seater Competition Sports, one of just five examples to get an Arnott Supercharger that enabled the 90-hp rating.
The youngest of the lot is a 1968 AC 428 Spider by Frua. Going back to the Ace, designer John Tojeiro took inspiration from the Ferrari Barchetta of the day. Pietro Frua's work on the 428 Spider eliminated the middleman for Ferrari-esque looks. Another Cobra connection is that this car started with the beefier Ford big-block 427 Cobra chassis, which AC extended six inches before sending to Italy for sheetmetal clothing. Although practically unknown now outside of devotee circles, this one found its first home with Rob Walker, heir to the Johnny Walker fortune, motorcycle and car racer, and motorsports team owner who employed drivers from Maurice Trintignant to Jochen Rindt and Stirling Moss. As with the other AC's, it's offered without reserve, the pre-sale estimate coming in at $350,000 to $400,000.