News & Features February 16, 2007, 2:19PM EST

Putting a Little English on a Chevy

In the 1970s Chevy hired British engineering firm Cosworth to design a high-performance version of the modest Vega—and succeeded

by B. Mitchell Carlson

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When Chevrolet's new compact, the Vega, came to the market for 1971, it was intended to compete with imports landing on both U.S. coasts.

Shortly before the car's introduction, then Chevrolet General Manager John Z. DeLorean directed his staff to develop a high-performance "halo car" variant.

One of the leads he suggested was Keith Duckworth of England's Cosworth Engineering, to see if they could develop a hot version of the Vega's newly developed aluminum four-cylinder motor. John Z thought the motor would form a good basis for a full race version, and in 1970, both Chevrolet and Cosworth started development work.

THE VEGA LAID AN EGG

Meanwhile, the production Vega was turned loose on the marketplace and laid an egg. Economy cars weren't trendy, let alone one with an all-aluminum engine (GM should've figured that one out from the Corvair).

On top of that, the "sporty" Vega GT was tanking, since it was nothing more than trim and decals, and those didn't count for much when sitting next to a Chevelle SS 454 on the dealer's lot. Good news was needed for the Vega line, so upper management put the heat on their engineering department and Cosworth to come up with a wonder motor.

However, at Cosworth, they were discovering what millions of Vega owners would eventually find out: the all-aluminum block was prone to failure. Developed by GM engineers with the assistance of Reynolds Aluminum, it was the world's first (and so far only) all-aluminum block, including the cylinder bores.

In lieu of steel sleeves, the block was cast from a high-silicon-content alloy, which initially seemed to wear at the same rate as steel. In reality, most engines started to wear out of tolerance within 40,000 to 50,000 miles. What Cosworth was also finding was that while they could develop gobs of power with their twin-overhead cam cylinder head (up to 290 hp at 9, 000 rpm); the blocks would break, especially at the bottom. Discouraged, and lacking the capacity for volume production, Cosworth licensed the head design to Chevrolet for further development.

COSWORTH DISCOURAGED

Despite this news, GM gave the Vega TC (its code-name internally) the green light. Sales were still sluggish, and the "race on Sunday, sell on Monday" mantra was deemed the Vega's best hope. In this case, racing was SCCA Production B sedan class, Chevy's target from nearly day one, due to what was happening both here and in European 2-liter class sports car racing.

Based upon computer models, the Vega TC was expected to be competitive, if not have a slight edge (being in a lighter body) than both the BMW 2002 and the Alfa Romeo GTA. Chevy's plan was to have at least 1,000 examples of the hot motor available in the Vega to homologate it for the series. Several forms of induction were considered. The best setup, with Weber sidedraft carburetors, was not in the cards, as the DCOEs could not be smogged (as BMW found out with the 1600ti, thusly creating the famous 2002).

The only carbureted variant considered for production used the Weber-designed, Holley-built DGAV-type progressive downdraft two-barrel. Fuel injection appeared the best bet, but GM's Rochester Products division was only interested in developing a complete integrated system (to include a sealed fuel system and catalytic converters).

Externally, systems from both Lucas and Bendix were considered, with the latter getting the nod for production. The engineers continued to improve the durability of the engine blocks, and the whole twin-cam program was targeted for the 1974 model year. Press releases, sales material, color and trim selections, and even a test by Car & Driver magazine were slated.

MOTORS DETUNED FURTHER

Increased emission regulations meant the motor needed to be detuned further. This was no easy task, as the package was originally designed for a 12:1 compression ratio and struggled at 8.5:1 and 110 hp--a far cry from 290. But what caused the missed production date was that the motor failed its EPA certification test, due to burned valves from an overly lean fuel mixture and advanced timing.