Why the ZL1 Corvette Is America's Sweetheart
In 1968, Car and Driver wrote that “the small-engine Corvettes are marginally faster and extraordinarily civilized. The large-engine Corvettes are extraordinarily fast and marginally civilized.” Depending on engine choice, a Corvette could have very different personalities. The small block cars had up to 350 horsepower in a well-balanced (especially for 1960's American standards) package. The big block cars could be officially had with up to 435 horsepower but those who knew their way around GM's RPO forms could buy much more.
The cost of adding 77 cubic inches came in the form of a major weight penalty. The big 427 weighed substantially more than the small block, and all that weight over the front wheels caused major under steer. The hot ticket would be a way to get big block power with small block weight. And that's just what Chevrolet did.
The ZL1 was essentially an aluminum version of the L88 7 liter big block. Officially rated at 430 horsepower, its true gross output was around 520 gross horsepower. A lightly de-tuned race engine, the ZL1 was barely tractable on the street. With a crushing 12.5:1 compression ratio and a massive 850 cfm carb, the ZL1 was truly a force to be reckoned with. People often wax poetic about "racecars for the street" but this truly was a slightly domesticated fire spitting racer in all its rough idling and hard starting glory. One customer replaced his L88 Corvette (essentially an iron block ZL1) with a Maserati Ghibli because he wanted something more reliable!
Though its price may have been hard to stomach, it's hard to argue with its brutal performance. A ZL1 with 3.70:1 gears and a four-speed ran the quarter mile in only 12.1 seconds! With the right gearing and a lot of guts, the ZL1 could have surely broken 200 mph.
To really demonstrate just how outrageous the ZL1 really was, we need to compare it against the best supercars the world had to offer in 1969.The Lamborghini Miura P400 S and Ferrari 365 GTB "Daytona" were among the fastest cars you could buy in 1969. Both sported exotic styling, DOHC V12 engines and price tags around double what a ZL1 Corvette cost. Of course it's hard to express the sexy, primal wail of a strung out V12 on a spreadsheet, but the chart does give a basic idea of how these three '60's supercars stack up.
While the ZL1's four-speed transmission didn't allow the top speed of the five-speed equipped exotics, it was nevertheless a legitimate competitor on a road course with its monstrous V8 making up for its marginal cornering ability.
Whereas the technically advanced and complex Italian supercars offered the full package of acceleration, handling and refined interiors, the ZL1 was a car built around the engine. The idea of being able to buy real race ready engines in production cars has almost completely died today. Try buying a 5.7 liter TRD NASCAR V8 in a Camry. Those days are all but gone, but the heavy drinking, street brawling ZL1 is proof that such beasts did, indeed, exist. As guitarist Slash once said "it seems excessive, but that doesn't mean it didn't happen".
Article Sources: http://www.camaros.org/copo.shtml, Corvette—Fifty Years by Randy Leffingwell