Chevrolet's Rochester Fuel Injected Passenger Cars

Fuel Injection For The Masses—1950’s-style

Robert Genat Sep 26, 2013 0 Comment(s)
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In 1955, Chevrolet hit a home run with its smartly restyled passenger cars (including the high-end Nomad wagon) and new 265ci V-8 engine. In 1956, Chevrolet hit a grand slam with its Zora Arkus-Duntov-conceived 225 hp dual-quad engine. And, if we may continue the baseball metaphor, they won the World Series with the highly styled '57 models, 283ci engine and Rochester fuel injection that produced a then-amazing 283 hp.

Chevrolet Chief Engineer Ed Cole's desire to have the first practical fuel-injected engine in an American passenger car was the driving force behind Rochester's unit. In '55, he assigned Duntov the task of developing a new fuel injection system. While Duntov gets high praise for his work on the Corvette, he always gave full credit to GM engineer John Dolza for his outstanding work on the Rochester fuel injection system.

The biggest advantage of fuel injection was not horsepower, but the ability to distribute the fuel-air mixture equally to all cylinders. Traditional intake manifolds are designed with a compromise between low- and medium-speed driving. Due to the length of the runners, fuel mixtures can vary as much as 15-percent between cylinders. Carburetors were also susceptible to fuel sloshing in small float bowls. This was especially bothersome to those who road raced and would find their engine starved for fuel after an especially hard turn and flooded after the next.

1961 Bruce Morgan Chevrolet Bel Air 1961 Pontiac 2/12

Rochester's fuel injection system consists of three main components: the intake manifold/plenum (also know as the "dog house"), the fuel meter, and the air meter. The intake manifold/plenum is the largest and most visible of the components. There are two pieces to the manifold, a base plate, which doubles as a valley cover (and for the injector nozzles), and the actual plenum. The plenum's job is to distribute air to the cylinders and serve as a mount for the fuel meter and air meter.

Rochester's engineers mounted the fuel meter to the right side of the plenum. This small rectangular component contains a large fuel reservoir with a conventional float, needle and seat, and a positive displacement high-pressure pump. A flex cable attached to the distributor drives this pump. It runs at half engine speed and pressures vary from 7.2 psi at idle to 530 psi at 6,000 engine rpm. The fuel from this pump is delivered directly to the nozzles.

The air meter is the third major component of the Rochester fuel injection system. It is mounted on the left side of the plenum. The air meter measures, controls, and delivers the air used in combustion. Its three main components are the throttle valve, the diffuser cone, and the air meter body, which contains the Venturi.

The distributors on all Rochester fuel injected engines were unique to that application. All were a two-piece design with a small flex cable drive that spun the fuel pump in the fuel meter unit. In 1957, all early fuel injected cars, both 250- and 283hp, were fitted with dual-point distributors with no vacuum advance unit. Later in the model year, Chevrolet changed to a single-point distributor on the 250hp engine with a vacuum advance. Between 1958 and 1962, all high performance fuel injected engines used dual-point distributors without a vacuum advance unit.

1957 Chevrolet 283 3/12

Driving a vehicle with a Rochester fuel injection system is a unique experience. When the accelerator is depressed there is an instant and smooth response, unlike a carbureted engine, where there is always a definite change in the acceleration sensation when the secondaries are opened. On any carburetor, that moment when the secondaries are about to open is always a difficult transition. With the Rochester injection, there is no tip-in point, only smooth acceleration throughout the entire range of the accelerator pedal.

1957

At $550, the cost for the fuel injection option (same for either the low- or high-horsepower version) on a '57 Chevrolet passenger car was steep. But many were sold, especially on the stylish Bel Airs and Nomad wagons. Those willing to shell out that extra money were rewarded with the most advanced engine available in a production passenger car. Chevrolet offered two injected 283s in '57: the hydraulic-cammed 250hp mill that could be backed by an automatic, and the 283hp option that required a manual transmission.

The '57 FI cars also displayed a crossed flags emblem and fuel injection script on the fenders. These were the same emblems used on the FI Corvettes. This is the first time that a modern manufacturer had added an exterior emblem that directly related to an optional engine on a passenger car. Chevrolet had been using a "V" emblem since 1955 to denote a V-8 engine, but nothing to indicate the induction system. The fuel injection emblems on the fender spoke volumes when a new '57 Chevrolet rolled into a drive-in restaurant.

1958

In 1958, Chevrolet rolled out a car that looked nothing like its '57 predecessor—it looked more Cadillac than Chevrolet. It was longer, lower, wider and decked with chrome. Chevrolet again offered two fuel-injected versions of the 283, both listing for $450, and both were identical to the fuel injected engines in the '58 Corvette except for the air cleaner and valve covers. The horsepower ratings were 250 and now 290 for the solid-lifter version, even though it was identical to the 283hp version sold a year earlier.

To meet the needs of its expanding truck line and future cars, Chevrolet's engineers created an all-new engine for '58 that displaced 348 ci. Initially in two horsepower ratings: 250 with a single four-barrel carburetor, 280 with tri-power and (later in the year) a 315hp high-performance tri-power version.

The buyer's dilemma became obvious: Why spend $450 for a 290hp fuel-injected 283 when you could have the 315hp tri-power 348 for only $162? Offering two V-8s could have been a selling point against Ford, but the internal complexity it created for Chevrolet and the extra consumer cost surely limited the orders of fuel-injected engines in full-size Chevrolets.

1959

In the late '50s race for bigger fins, Chevrolet went all-in with its gull wings and cat's eye taillights. Performance was still a big part of Chevrolet's business plan and the two optional fuel injected engines (250 and 290 hp) remained on the option list. But its cost and complexity pushed potential buyers away. Those who were looking for performance could select one of the several less expensive 348ci engines.

Chevrolet didn't offer a fuel-injected engine for its passenger cars in 1960, but the FI option continued in Corvettes for years. In 1961, the last year for the 283, Chevy's engineers pulled a robust 315 hp out of its FI engine. The addition of the 327 in 1962 allowed Chevrolet's engineers to crank out 360 hp. In 1965, its last year as a Corvette option, the fuel-injected 327 produced 375 hp—the high water mark for the first-gen SBC.

While always overshadowed by big-block horsepower, Chevrolet's Rochester fuel injection is one of the cornerstone pieces that made up Chevrolet's performance pyramid. And even today, a car with one of these Rochester units still has the ability to draw a crowd at a car show like a fight in a schoolyard.

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