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With the 1966 Corvette arriving after General Motors recent, overwhelming success with the 427 Sting Ray, there was no question that the newest Corvette model would continue to feature big-block engines. This turnabout in events was rather interesting, especially given GM management’s earlier decree that no car line smaller than a full-size model would carry an engine larger than 400 cubic inches. Perhaps fortunately for Corvette, it was Carroll Shelby’s two-seat Cobra, which featured its own 427 cubic inch V8 engine that prompted the change of opinion. Chevrolet now felt it would also need a 427 cubic inch engine, and it materialized for the 1966 model year.
Although it was effectively a 396 cubic inch engine with a larger 4.25-inch bore, the new 427 big-block engine came in two forms: the relatively mild L36, which featured a hydraulic-cam and produced 390 horsepower on 10.25:1 compression, and the truly awesome L72, a 425 horsepower engine with 11:1 compression, larger intake valves, a bigger Holley four-barrel carburetor on an aluminum manifold, mechanical lifters, and four-hole (instead of two-hole) main bearing caps. Though it had no more horsepower than the previously developed 396 cubic inch engine, the 427 did pack quite a bit more torque-460lbs/ft instead of 415. Given the fact that, especially in the Sixties, engine outputs were sometim
sometimes deliberately understated, it is not unreasonable to assume that the output of these two engines was closer to 420 and 450 horsepower respectively.
There were limitations to ordering the big block 427 cubic inch engine. First, it had to be ordered in combination with Positraction and the close-ratio Muncie four-speed transmission. It also required that the Corvette was equipped with an upgraded suspension, similar to the setup on the 396 package. Lastly, it required stouter, shot-peened halfshafts and U-joints, as well as a higher-capacity radiator and sump.
The introduction of the big-block V-8 engine captured the imagination of Corvette consumers the world over, and in no time at all, the demand for big-blocks far surpassed those of the conventional 327 small block Chevy engine. As a result, the small-block engine options were reduced from five to two for the 1966 model year, with only the 300-horsepower (L75) and 350-horsepower (L79) versions remaining available to prospective consumers. Even amongst the earlier small-block options that had been available on earlier Corvettes, these two engines were arguably the best all-around engines. Additionally, both could be paired with the Powerglide automatic, the standard three-speed manual, or either of the optional four-speed manual transmissions.
With the exception of the dramatic new lineup of engine choices, there was little else that was deemed “new” for the 1966 model year. There were minor modifications made to the Corvette’s appearance. For one, the Sting Ray’s front end was mildly altered with the introduction of an “eggcrate” grille insert which replaced the previously installed horizontal bars. Restyled wheel covers were introduced along with an all new rocker trim. Also, the coupe lost its roof-mounted extractor vents, which had proven to be inefficient on earlier model years. Lastly, less notable upgrades like the addition of “Corvette Sting Ray” scripts to the hood and the introduction of standard backup lights were introduced.
Likewise, the interior went largely unaltered from 1965. The interior electric ventilation system was dropped (in conjunction with the aforementioned exterior vents), extra pleats were added to the Sting Ray’s bucket seats, chrome door pull handles were introduced, headrests were made optional, and a vinyl-covered foam headliner replaced the previously used fiberboard. Given that these were amongst the only notable changes from 1965 to 1966, there was a good deal of reasonable speculation that an all-new Corvette was slated for 1967.
Still, the lack of changes for the 1966 model year did not hurt the Corvette’s popularity with consumers. In fact, 1966 would prove to be another record-breaking year in Corvette sales, with volume rising to 27,720 units sold – an increase of more than 4,200 units over 1965’s sales of 23,562 units. Consumers found that the new Corvette, especially one equipped with the 427 big-block, had all the refinement it needed. The 427 Sting Ray was an astonishingly fast car, with 0-60 times of just 4.8 seconds, 0-100 mph times of 11.2 seconds, and a top speed of 140 miles per hour (when properly equipped with the short 4.11:1 gearing.) Even in cars equipped with the somewhat less sensational 3.36:1 ratio, the Corvette was still able to run 0-60 times of 5.4 seconds with a standing quarter of 12.8 seconds at 112 miles per hour (source Car and Driver).
Impressive as those numbers were, the intent of the 427 cubic inch engine had been to meet the Shelby Cobra head-on and give it some staunch competition. However, even despite the staggering horsepower and the impressive performance numbers, the fact remained that the Corvette was a half a ton heavier than the Shelby Cobra so, even with the same horsepower rating, it was considered less than a threat. Still, the Corvette did not go home empty handed. The Corvette still took a number of victories in endurance racing including Penske’s team’s 12th place overall in the GT class.
1.) The Pocket Book of the Corvette: The Definitive Guide to the All American Sports Car - Copyright 2003, Barnes & Noble
The 427 cubic-inch engines were introduced in the 1966 model. Corvettes equipped with this type of engine received a special bubble hood first seen on the 1965 Corvettes equipped with the 396 cubic inch engine.
Although initially listed as a 450hp engine, the solid lifter 427ci engine's rating was later reduced to 425hp shortlly after its introduction for reasons unknown.
Similarly, the 390 horsepower engine was initially rated at 400 horsepower.
When the official ratings were reduced, the decision to make this change was purely administrative and was not the result of any changes made to the engines.