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Hot Rodding Chevrolet’s Small-Block V-8, Circa 1955

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Drew Hardin Feb 21, 2017
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While the public’s reception of the radically redesigned 1955 Chevrolet was somewhat lukewarm (at least at first), the high-performance industry took an immediate interest in the 265ci overhead valve V-8 engine that Chevrolet introduced with it. Several engine builders and race shops made arrangements with Chevy to get pre-production engines in their hands for R&D work prior to the new car’s launch.

One of those was Vic Edelbrock Sr., who took delivery of three crate small-blocks for development work. His main priority, interestingly enough, was to evaluate the engine for use in hydroplane racing, where his Ford flathead V-8s were enjoying a lot of success. Hot Rod magazine’s Racer Brown was present for much of the testing Vic Sr. (and Jr.) did on one of those engines and chronicled the work in depth in a Jan. 1956 article titled “229 Horsepower Chevy V-8.” (Spoiler alert.)

The Edelbrock team tore down the engine, measured and cleaned all its components, and then put it back together with a balanced reciprocating assembly and cylinders bored slightly to increase piston-to-cylinder-wall clearance. On Edelbrock’s Clayton 300hp dynamometer, the optimized (but still stock) engine made 135 hp at 4,500 rpm.

The upgrade testing began with the replacement of the stock two-barrel Rochester carb and intake with Edelbrock’s brand-new triple-carb manifold and three Rochesters. On the dyno peak output rose 20 percent, to 163 hp at 4,500 rpm. Removing the stock exhaust manifolds and adding a custom set of Hedman headers saw another significant uptick in power, to 173.

At this point Edelbrock made some modifications to the heads. The intake and exhaust ports were enlarged, the valve pockets were ground out, the ports polished, and the valves treated to “a first-class valve job,” said Brown. The result was 176 peak hp.

Next, Edelbrock installed what Brown described as a “Corvette” cam, valvesprings, and lifters. The cam provided 0.394/0.383-inch lift (intake/exhaust) and 296/287 degrees of duration. At 4,500 rpm, where the small-block had peaked previously, hp was measured at 192, but the engine wasn’t done yet; power topped out at 205 hp at 5,300 rpm. “Just for the record,” the Edelbrock triple-deuce manifold was swapped for a stock Chevy intake and four-barrel Carter carburetor, resulting in a drop in peak hp to 181 at 4,800 rpm. At that point in the process Edelbrock began evaluating some 20 different camshafts they had collected from “reputable cam grinding establishments” to test for maximum power and engine speed. Brown declined to name the cam companies “in order to prevent any thoughts of discrimination.” But in Tom Madigan’s book Edelbrock: Made in USA, the grinders were identified as including Ed Iskenderian, Clay Smith, Jack Engle, Ed Winfield, and others. Brown said “some pretty weird engine performance characteristics came to light” during the cam tests, and he regretted not having the space in the magazine to present all the data. “Maximum power varied all over the map,” he said, and “several cams showed some pretty violent harmonic vibration tendencies, or ‘surge’ in the valvespring department, which prevented accurate power and engine speed readings.” In the end, “cam test seven” was the “most satisfactory from all standpoints,” Brown wrote. Power peaked at 229 at 5,850 rpm, which was the “highest power and peaking speed of any cam tested.” Low speed power output was “better than average,” and “the idle was merely bad instead of horrible.” This cam spec’d at 0.410-inch lift and 256 degrees duration. Brown, of course, didn’t identify the winning cam grinder. But Madigan reports it was “Vic’s old friend Ed Iskenderian who was chosen to develop the camshaft.” In the end, Brown called the small-block “a very rugged and thoroughly dependable powerplant. When modifications are properly administered, the engine is amazingly responsive.” Words true to this day still.

Archive Edelbrock Small Block Engine With Dial Indicator 2/5

“Chevy pulley was fully degreed,” Racer Brown wrote of the test engine setup, “necessary for indexing cams, setting ignition timing.”

Archive Edelbrock Small Block Hedman Headers 3/5

Custom-made Hedman headers “proved to be worth price,” adding 10 hp.

Archive Edelbrock Small Block Pistons 4/5

“Nicks in the pistons are proof that interference existed with all valves.”

Archive Edelbrock Small Block Senior Junior 5/5

“A most talented father/son team,” as Brown described them. “Vic Jr. did the work, was supervised by his dad.”

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