Curbside Classic: 1976 Cosworth Vega #2196 – Muscle Memory, In Honor of the Vega’s 50th Anniversary

But back in London, Cosworth had hit a ‘stumbling block’ with the EAA engine. Mike Hall, Cosworth’s engineer responsible for the BD-series engines, commented, “It was extremely light compared to the BDA with its pressure die-cast aluminium block from Reynolds, but was not up to the ratings we were putting through it. Designed to be a two-litre racer, we could not make the cylinder block live. There was nothing we could do.”

Cosworth’s head of Sales, Jack Field, stated that, “Cosworth stopped development of the Cosworth Vega F2 – Sports Racing engine when GM wouldn’t update the block to keep it from coming apart. Experience with the engines confirmed the block was fragile. The top separated from the bottom. A crack would originate from the water pump opening and travel toward the rear of the block on the left side. The crack would either let the coolant out or worse let the oil out by cracking the main oil feed galley. The resultant oil spray would get on the headers and a fire would follow.”

Chevron B21

Lola T290

Chevy-Cosworth EAA engine as installed in Lola T290

Primarily used in Chevron B19, B21 and Lola T290 race cars during the 1972 and 1973 racing seasons, the engine’s light weight and power output made it a formidable competitor, with EAA-powered cars racking up a respectable number of wins and top-ten placements when the engine held together. But for the block’s weaknesses and other teething issues, it could well have pulled off DeLorean’s plan to dominate European F2 and SCCA “B” Production class racing.

A history of Cosworth Engineering written in 1988 recounts that, “Hundreds of blocks were being delivered, many failing a pressure test Cosworth devised for them and littering up the place while a solution was found. It never was. Those which passed the test were released, the first version stirring in anger in Guy Edwards’ Lola but failing to go the distance despite the attentions of Messrs. Duckworth and Scammell at Salzburgring.”

Accounts from EAA-powered drivers and crew indicated the engine would typically fail after 2–3 hours of racing. These engines were making 270 HP as previously mentioned. The consensus was that the stock block could handle up to around 250 HP when running longer duty cycles. GM did respond, belatedly, to the cracking problem by tooling up and manufacturing 50 units of an HD version of the block with extra ribbing.

But by 1973, Cosworth had had enough and pulled the plug – the EAA race engine project was dead. A number of the HD blocks subsequently found their way into hill climb, USAC Midget and IMSA RS Vega cars, and proved to be reliable and competitive engines in those applications.

Before we return to development of the street version of the Cosworth engine, it’s worth taking a moment to briefly touch on other engine options being considered for Vega in this timeframe. Per Ed Cole’s request, the Vega had been developed to accept a V8 engine, and a single prototype was built using an all-aluminum engine that was the last of several 283 cu in (4.6 L) units from the CERV I Corvette R&D program. Bored out to 302 cu in (4.9 L) and mated to a Turbo Hydramatic automatic with a stock differential and street tires, the car yielded quarter mile (~400 m) times under 14 seconds in Hot Rod magazine’s July 1972 road test of the prototype. That GM was seriously considering a V8 option is confirmed by the fact that early-production Vegas used transmission crossmembers with clearance reliefs for dual exhaust pipes.

Additionally, GM had been busy working on its RC2-206 rotary engine, with intent to offer it in the 1974 Vega as documented in the May 1972 issue of Popular Science. In fact, GM had done durability testing of RC2-206 Wankels fitted in 1973 Vegas, but then decided to instead offer the rotary in the H-bodied Monza 2+2 – early-production Monzas had a wider transmission tunnel to accommodate the planned rotary. But it was not to be, as Ed Cole postponed the rotary program in September, 1974, retiring from GM the same month. Pete Estes, his successor, had little interest in the engine and the program was canceled in April, 1977 despite data from the R&D team indicating they felt they had solved its fuel economy and durability issues.

As an aside, development of the Monza started in 1971, well before Vega’s problems were widely known – Monza was not a response to Vega’s failures, but rather an attempt at a more upscale and exotic offering aimed at a market slot above the Vega.

Bill Mitchell couldn’t resist getting in on the act, either, with his ‘CorVega’ image car shown at the 1971 New York Auto Show. Originally powered by a turbocharged 2300 engine, the car was later completely revised with a Cosworth Twin Cam engine and distinctive bodywork.

Finally, I would be remiss if I didn’t also mention the XP-898 concept from early 1973. While the body was completely original and made of innovative foam-filled molded plastic, all of the running gear was stock Vega. The one drivetrain exception was the engine, which used the stillborn cross-flow aluminum head that Chevrolet had developed. Power was better, NVH was reduced and the engine was a full 4” shorter than the stock Vega unit, allowing for a much lower hood line. Ah, well…

In early April, 1972, Ed Cole had test driven three Vegas including a stock base-trim car for reference, the prototype V8 car and a prototype Cosworth Twin Cam Vega fitted with dual Weber-Holley two-barrel carbs making 170 HP gross (about 130 HP net) and 125 lb-ft torque. He loved the Cosworth and offered his support for a run of 5,000 Twin Cam Vegas. Even Zora Arkus-Duntov was impressed with the Cosworth, stating it was ‘nicest 4-cylinder’ he had ever driven. DeLorean got his first ride a couple months later and signed off on development toward EPA certification and production. While two cars were prepared for 1973 emissions testing, they were never submitted as engineers were still working to sort part-throttle drivability and emissions issues. Further work was done on the cam profiles and to improve the torque curve, the cast iron exhaust manifold was swapped for a tubular stainless steel header to improve low-RPM drivability as noted above.

All this work delayed the program past the point where they could make the 1973 model year, so the new target release was 1974. Seven pilot build cars were assembled in April, 1973, all wearing silver paint and bearing COSWORTH VEGA 16 VALVE decals on their front fenders. Chevrolet Public Relations began teasing the upcoming limited-edition Cosworth Vega, with a formal announcement for the 1974 model year occurring in July of 1973. The car’s design had been frozen by this point, with the color scheme being revised by GM designer Jerry Palmer to black (a color unavailable on other Vega trims until 1976) with gold accents, bearing the COSWORTH TWIN CAM name on the fenders, engine cam cover, horn button, wheel center caps and on a plaque indicating the car’s build number fitted to the unique gold engine-turned dash panel. John DeLorean would not be around to oversee the final development of the car, however, having resigned from GM in April.

Enthusiastic reviews started to pour in from the trade rags, and in January, 1974, Car & Driver’s test of a Pilot build Cosworth Vega turned in the fastest 0-60 MPH time (7.7 seconds) of any car they tested that year (keep in mind, this was right at the beginning of the Malaise Era and the lightweight Cosworth was still making 170 HP gross at this point).

Finally it was time to run the car through the 1974 EPA test cycle. It’s an oft-repeated fact that two of the three test engines failed the test cycle. The backstory is that a decision was made (strenuously fought against by the Vega TC engine team) to significantly retard the timing in order to provide a margin of safety in the emissions results. This created excessive heat that caused failure of the exhaust valves and seats at around the 46,000 mile mark in the 50,000 mile test. The engine team was bitterly disappointed, feeling that the engine would easily have passed using the recommended timing settings.

The whole EPA test cycle, including months of durability tests, would have to start over from scratch – and would have to meet even tighter 1975 regulations. The Bendix electronic fuel injection system was revised to improve air distribution, and a Pulse Air system was added – this system did the same job as an A.I.R. pump, but without the pump’s 6 HP penalty (note that Pulse Air is different from an EGR system). High-energy ignition was added, and the timing was advanced, which, along with the requirement of lead-free fuel, ensured everything would work well with the now-mandatory catalytic converter. Internal Chevrolet testing required an engine be able to survive 200 hours at full load – the Cosworth engine went over 500 hours. Cal Wade even ran a test engine up to 9,400 RPM in a clutch burst test and the engine survived just fine (as did the clutch).

Three cars began durability tests in September, 1974 (the same month Ed Cole put the rotary engine program on hold and subsequently retired), each configured differently to ensure at least one would pass. Testing completed in January, 1975, and one of the three configurations met California’s tighter limits for 1975, so this configuration became the one used in production, making the Cosworth Vega the only GM car to be 50-State compliant. In fact, all three test cars came very close to meeting 1977 Federal standards.

In February 1975, five Pilot cars were built at the Lordstown plant. The first RPO Z09 production car was built on March 27, 1975 and on April 17, 1975, a media event was held at Lordstown, where the Cosworth Vega began rolling off the line at approximately 1.67 cars per hour on two shifts – two-and-a-half years after the original planned launch date.

A total of 5,000 Twin Cam engines were hand-assembled (and signed by the builder) in batches of 30 in a clean room at the Tonawanda, NY facility originally set up for assembly of all-aluminum ZL-1 427 cu in (7 liter) V8 engines. As an interesting historical aside, five low-mile used Cosworth Vega engines were purchased to use for reference by the Oldsmobile Quad 4 development team.

The Cosworth Vega was finally here, but reviews were not quite as gushing as they had been for the scrubbed 1974 model. Power was down to a mere 110 HP (net) at 5,600 RPM and 107 lb-ft torque; the compression ratio had dropped all the way down to 8.5:1. The 1975 Vega GT engine made 87 HP (net), so you got about 30% more power with the Cosworth, but that same Vega GT engine also made 14% more torque, at 122 lb-ft. The heavier 1975 Monza (called the ‘Italian Vega’ by DeLorean) launched with the same 2300 engine used in the Vega, but was also available with a 262 cu in (4.3 liter) V8, also making 110 HP (net), and if you lived in California, your V8 Monza came with a 350 cu in (5.7 liter) V8 making 125 HP (net).

110 HP may sound anemic, but power was down across the board throughout Chevrolet’s lineup due to 1975 emissions requirements. The L-48-powered Corvette (165 HP) was only slightly faster to 60 MPH, and a V8-powered Camaro (145 HP, but almost a half-ton heavier) took 10.9 seconds to achieve 60 MPH compared with the 8.7 seconds recorded by Car & Driver in a 1976 Cosworth Vega.

Where the Cosworth Vega positively excelled was in handling, partly because it received the revised rear suspension used in the heavier Monza. The Vega had always been a good handler if optioned right – Road & Track in 1973 reported, “With these tires (BR70-13) the Vega does better on the skidpad than every other car in our test summary except the Jaguar XJ6, very select company indeed. It also outdoes the ’73 Corvette on its radials in this particular test.” Reviews quickly racked up touting the Cosworth Vega’s agility: Car and Driver reported in October 1975, “As quick as the lil’ black Vega is in a straight line, it would be a big mistake to use one as a straight-line machine. The car’s forte is a nice, winding road. The sort of place you don’t see jacked-up Road Runners with drag slicks. This is where the Cosworth really shines. At moderate speeds, the car is as close to neutral handling as any American car I have ever driven … The outstanding feature of the Cosworth Vega is its excellent balance. Roll-stiffness distribution is ideal, with little understeer entering a turn, and just the right amount of drift from the tail as you put your foot down to exit.”

Road Test magazine’s October 1976 ‘Great Supercoupe Shootout’ pitted an Alfa Romeo Alfetta GT, Mazda Cosmo, Lancia Beta and Saab EMS against the Cosworth Vega and found that, “The Chevrolet Cosworth Vega is the only American car worthy of the lot. It is more than just some little super coupe … Read ‘em and weep, all you foreign-is-better nuts, because right there at the top, and by a long way at that, is the Cosworth Vega. It had the fastest 0-60 time, the fastest quarter-mile time, and tied with the Saab for the shortest braking distance … The Cosworth is American, and a collector’s item, and it came close, damn close to winning the whole thing.”

But despite the sparkling handling, and the fact it was the first American mass-produced automobile to feature a DOHC 4-valve, 4-cylinder engine, the first Chevrolet with electronic fuel injection and the first Chevrolet to use pressure-die-cast aluminum wheels, there were precious few takers. The price was certainly eye-watering; another $800 or so would put you in a Corvette, and Chevrolet even had the chutzpah to advertise the car as “One Vega for the Price of Two.”

Dealers were told to “play hard to get” – the thought being that having a Twin Cam in the showroom as bait would bring in customers that could be switched over to other Chevrolet offerings – these dealers often ended up sitting on cars long after they were canceled, eventually selling them at a loss. At least one dealer went so far as to fit Landau roofs on a few cars in hopes of finally moving them off.

After having moved only 2,061 units in 1975, changes were made in hopes of generating higher interest. Eight additional exterior colors were added, along with a number of additional interior color and material options. Along with the new grille and rear taillights that all 1976 Vegas received, the Cosworth got upgraded brakes, softer springs and a 1” higher ride height. An optional Borg-Warner T-50 ‘dogleg’ five-speed transmission paired with a 4.10 ratio differential was added and the 1975’s dual-outlet tailpipe was revised to a single outlet. 1976 sales were dismal none-the-less; only 1,447 units were sold (for a total of 3,508) before the plug was pulled for good. GM broke down 500 leftover Twin Cam engines for spares and destroyed the rest.

45 years later (as of this writing), the Cosworth Vega remains – aside from a small pocket of enthusiasts – an outlier in the collector market, despite being one of the rarest Chevrolet cars ever made. Many have of course succumbed to the ravages of time, hooning, accidents or V6 and V8 engine swaps. A variety of other engines have found their way under Cossie hoods including an Ecotec, a Mazda rotary and a 3.0 litre Cosworth V6. Non-runners may sell for a couple thousand or less, and a decent driver-quality car can be had for $6-8K. The current upper end of the market was set recently when 1976 Cosworth Vega #3037 sold on Bring A Trailer for $48,000 – this car had a mere 39 miles on both the odometer and the originally-fitted Goodyear BR70-13 tires. But there aren’t many Cossies left in that kind of time capsule condition…

Pages: 1 2 3