Steve Magnante's 1001 Corvette Facts. Steve Magnante

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СКАЧАТЬ on a V-8. The extra breathing helped boost output from 210 to 225 hp. The base-Corvette V-8’s single Carter WCFB 4-barrel was bolted to a cast-iron intake manifold.

      180 Fuel injection was added for 1957, but unlike the modern electronic-fuel-injection (EFI) systems we use today, the Ram Jet fuel-injection unit was mechanical. That is, instead of having an electric fuel pump and electronically cycled solenoid-style injectors, the pump was driven (at half engine speed) by a cable attached to the ignition distributor housing. The injectors were simple nozzles inserted near the base of the manifold runners and were always open for a constant-flow system.

      181 With the mechanical fuel pump driven by the distributor shaft, it delivered fuel pressure the entire time the engine was running. A three-piece bypass valve assembly regulated the pressure of fuel delivery. An air meter sensed engine vacuum (throttle position) and signaled the pressure regulator to direct full fuel flow to the nozzles (for power) or return some of it to a reservoir (light load, idle). Fuel pressure ranged from about 3 psi to 200 psi.

      182 The primary goal of the Rochester fuel-injection system was to eliminate the fuel-slosh problem encountered with carburetors on road-race circuits. All Corvette carburetors relied on integral reservoirs (called bowls) to maintain a steady supply of gasoline, ready to be drawn into the engine by vacuum. However, during hard corners, lateral g-forces could pull the raw gasoline away from metering orifices and cause fuel starvation and power loss/stalling, not the way to win races. With its constant, pressurized flow, mechanical fuel injection (and modern EFI) was a solution.

      183 Although GM’s primary goal was improved road-race results, it just so happened that fuel injection, with its (potentially) more precise fuel metering, could also improve fuel economy, reduce tailpipe emissions, and eliminate the cold-start hassles involved with certain carburetors and choke assemblies. A properly tuned Rochester fuel-injected Corvette (offered from 1957 to 1965) generally gave better fuel economy than its carbureted siblings and started more easily on frigid mornings.

      184 Airflow passing through the large, single venturi air meter gave fuelie Vettes a characteristic whistling sound at idle and during low-speed cruising. It was a detail that frustrated certain fuel-injection owners hoping to lurk undetected on the stoplight drag-racing circuit. They could remove the emblems, but the sound gave them away.

      185 Another benefit that General Motors took advantage of when designing Rochester fuel injection was how the system allowed for the benefits of ram tuning to be harnessed. On virtually every reciprocating engine using intake ports and runners to deliver the fuel-air mixture to the backs of the intake valves, there exists the opportunity to manipulate the incoming column of fuel for enhanced performance. Because this column is rushing toward the intake valve at 1,100 feet per second when the engine is at 6,000 rpm, it contains energy. If the length, volume, and shape of the intake runner and port are manipulated, the amount of energy in this slug of incoming fuel air can be harnessed for a mild form of supercharging. Chrysler adopted the ram-tuned intake-manifold concept in 1960 on everything from the Slant Six Valiant to the mighty Chrysler 300F. But in 1957, only Chevrolet (and Pontiac’s FI Bonneville) were using the ram-tuning concept on regular production models.

      186 The ram-tuning magic happened in the unique dog-house upper intake manifold atop every Rochester FI Corvette engine. Arkus-Duntov and the Rochester engineers wanted to boost the 283’s modest low-end punch, and they calculated that 11-inch-long runners would do the job. These runners were present inside every Rochester dog house but were only visible on 1963–1965 fuelie units. Rochester redesigned these later plenum boxes with a two-piece construction. Unscrewing the lid allowed inspection of the ram tube inlets.

      187 1961 brought a significant weight reduction for 4-speed buyers in the form of a new cast-aluminum transmission case for the Borg-Warner T-10. Although it was relatively unchanged internally, switching from cast iron shed about 30 pounds. The base cast-iron 3-speed manual transmission was never upgraded with an aluminum case and remained this way through its discontinuation after 1969.

      188 The 2-speed Powerglide automatic transmission also underwent a serious diet in 1962. GM’s Hydramatic division invested millions to switch from cast-iron to aluminum construction, which was a key component of Chevrolet’s all-new Chevy II/Nova compact car (in which weight was minimized). Corvettes benefitted from a 50-pound weight reduction.

      189 1960 brought lightweight aluminum construction to the clutch housing on 3- and 4-speed manual-transmission cars and the radiator unit on dual-quad and fuel-injected applications. Although replacing the traditional brass-and-copper radiator shed nose weight for improved handling, the lighter clutch cover was a mixed bag. After removing the stronger cast-iron case surrounding the spinning flywheel and pressure plate all that remained between flying clutch debris and the passenger compartment was a thin fiberglass floorboard. Serious Corvette racers quickly adopted aftermarket blow shields for improved safety.

190 Another aluminum item planned for 1960 that never materialized in dealer showrooms were the much-celebrated RPO 579/579D aluminum cylinder heads. Numerous enthusiast publications sang their praises, and official Chevrolet sales literature even announced them. British industry publication The Autocar reported in its December 25, 1959, issue that casting flaws were the killer, saying, “Heads tend to crack around (rocker arm) stud bosses. On a recent production run they got only two good heads out of 140!”

      191 Before 1962, carbureted Corvette engines used a generator-mounted cable to drive the tachometer. In contrast, most fuel-injected cars fed the tach from a cable run by the distributor. The trouble with the generator-driven tachometer was that a loose fan belt caused slippage. Precise, instantaneous monitoring of crankshaft speed was not possible with a slipping fan belt. Chevrolet corrected the situation in 1962 by upgrading all Corvette engines to distributor-driven tachometers.

      192 The fuel-injected 1957–1961 Corvettes built with generator-driven tachometers were the milder versions. With their lower compression ratios, relatively conservative cams, and hydraulic lifters, rapid RPM surges weren’t as much of a threat as they were with the top-tier fuelie engines, whose elevated compression ratios, more radical cams, and high-revving solid lifters more easily slipped fan belts, sending delayed and inaccurate engine RPM info to the driver. Moreover, 1961 was also the first year Chevrolet barred the mating of fuel-injected engines and Powerglide automatic transmissions. From 1961 to 1965, every fuelie was backed by a manual transmission.

      193 The 3-speed manual transmission offered for the first time on 1955 Corvettes was not a derivative of the Muncie 318/319 unit used in passenger cars since 1940. Rather, it was manufactured by GM’s Saginaw Gear division and featured unique ratios of 2.20:1, 1.30:1, and 1:10. Passenger cars from 1955-on (also) using this new transmission were equipped with 2.94:1, 1.31:1, and 1:10 ratios. The 2.20 First gear ratio offered less torque multiplication than the 2.94:1 passenger-car ratio but was offset by the Corvette’s 500-pound-lighter mass. The benefit of the 2.20:1 Low-gear ratio was that it suffered less of the RPM drop encountered during upshifts, and thus kept the engine closer to its power band when driven with a heavy throttle foot. Of the 3,467 Corvettes built in 1956, only 1,878 were equipped with this new 3-speed manual. Unfortunately, this new transmission lacked synchromesh in First gear.

      194 All 1953–1955 Corvettes came with a 3.55:1 rear-axle ratio, regardless of engine or transmission. For 1956–1961, the 3.55 ratio was standard only with the Powerglide automatic. For 1961, manual-transmission-equipped Corvettes came standard with slightly deeper 3.70:1 gears to bolster off-the-line torque multiplication. Optional rear-axle ratios also arrived in 1956 and included 4.11 and 4.56 ratios. For reasons unknown, the overdrive-equipped 3-speed stick available on passenger cars was not available in Corvettes. Although acceleration with 4.11 or 4.56 gears was thrilling, highway cruising at 3,800 rpm could be loud and tiresome. In 1961, a 3.36:1 gear-set option arrived for buyers less concerned with acceleration than with calm highway cruising and improved fuel economy.

      195 In 1962, the standard СКАЧАТЬ