To contemporary eyes, nothing seems small about 1958 Chevrolets. But put the car next to the imposing figure that was Hot Rod’s technical editor Ray Brock (all six feet, two inches of him), and the magazine can rightly say the all-new Chevy Impala “displays a low silhouette,” even with a roof height of 4 1/2 feet.
Automakers like to throw around the phrase “all new” every time they make even a few refinements to a model. But in this case, Chevrolet’s sedans were truly redesigned from the frame up. The previous year’s ladder-style chassis was replaced by framerails with a central X-member that was “very resistant to the twisting forces that are transmitted to it,” wrote Brock in Hot Rod’s Dec. 1957 issue. In addition, the new frame’s “low-slung design permits minimum overall car height while also providing plenty of foot room for rear seat passengers.”
The front suspension “is about the only part of the new Chevy that resembles the ’57 models,” he said, describing the unequal-length A-arms and coil springs. New for the year was a front stabilizer bar for all V-8 models (but absent from six-cylinder cars).
The rear suspension, though, was something “you haven’t seen on any car before,” Brock said. Coil springs sandwiched between “horseshoe shaped” upper control arms bushed to the frame and the center of the axlehousing, and lower control arms that ran from brackets just behind the X’s center to a second set of brackets welded to the ends of the axlehousings. “The linkage arrangement between the control arms and the axle is such that torque and braking forces are taken by the control arms, with ‘nosedive’ on stops and ‘squatting’ on acceleration almost completely eliminated. The ride is excellent through all types of dips and rough road.”
Something “that should be particularly helpful to those interested in drag racing…is the Positraction limited slip differential,” Brock wrote. This new-for-1958 option “gives full two-wheel traction on all types of surface but allows a differential between wheel speeds for normal cornering,” he explained.
“Moving to the engine department,” Brock mentioned the 235-inch six-cylinder briefly before discussing the “refined” 283-inch V-8 and why the top two options, the dual-quad and fuel-injected versions, had lower horsepower numbers (245 and 250, respectively) than the 1957 versions. “First, all of these passenger-car engines have hydraulic lifters, therefore a milder cam than the mechanical cam used in the ’57 performance models and secondly, you’ll notice that 9.5 to 1 is the maximum on compression, even with the injector.” Only the Corvette could get a 10.5:1 small-block and the resulting 290 horses.
“Now we get to the part a lot of you have been waiting for,” Brock said, saving the news about the all-new 348-inch engine for last. “This is not just a bored and stroked version of the 283 V-8, although lots of pieces from the two engines resemble each other.” He pointed out that the intake manifold forms the top engine cover, the distributor is at the rear of the block, and the fuel pump is at lower right. The 348, though, was longer, wider, and about 100 pounds heavier than the 283, the latter stat one of the reasons the engine wasn’t offered in the Corvette. (It would “upset the superb balance of the car,” he said.)
Two of the story’s eight pages were devoted to the 348’s construction, including its “odd-shaped rocker arm covers.” With a single Rochester or Carter four-barrel carburetor the engine was rated at 250 hp at 4,400 rpm and 355 lb-ft of torque at 2,800 rpm. An optional triple-two-barrel carburetor setup “identical in operation to Oldsmobile’s J-2 and Pontiac’s Tri-Power triples” brought power up to 280 horses at 4,800 rpm. Peak torque remained at 355 lb-ft, though it came in higher at 3,200 rpm.
“Only one cam is available for the 348 engines,” noted Brock. “And although it looks good on paper, a racing grind should help considerably, especially with the three two-barrel carburetors.”
Another hole in Chevy’s 1958 offering: “You cannot order an overdrive with the 348 engine. Sounds strange, but that’s the straight scoop. Too bad, because the 348 engine with triple carburetion, stick shift, overdrive, and a 4.11 rear axle should make quite an automobile.”
Wait til he gets his hands on a 409….
Courtesy of Petersen Publishing Co. Archive