Leading a Horse to Water
When it comes to cooling, you absolutely must figure out a way to bring the air to the cooler. The idea is, of course, to provide a constant supply of air through the radiator so that the coolant is reduced in temperature. Increasing the airflow through the radiator improves the cooling and, as a result, a shroud is almost mandatory on high-performance applications. Unfortunately, they're often missing on older Corvettes. Keep in mind the shrouds were often manufactured from plastic and, as a result, the condition typically degrades dramatically over the years. On a similar note, Corvettes that were raced seldom have them (for example, L88 models). If you don't have a shroud or if it fits poorly, get the right one (that's a big hint if you end up sitting behind Old Faithful on a regular basis).
How does the shroud work? Basically, the shroud surrounds or partially surrounds the fan. It butts up tightly to the face of the radiator, effectively sealing the cavity. This isolates the pocket of air behind the radiator, allowing the fan to efficiently draw the required air through the radiator. If the shroud is not present, it creates a considerable amount of dead space behind the radiator that in turn destroys the effectiveness of the fan assembly. The bottom line is simple: If you don't run a proper shroud, you're only asking for overheating grief.
In the case of electric fans, you usually have two options: a pusher fan or a puller fan. Chevrolet has used both configurations in modern passenger cars, Corvettes, and light trucks, although puller fans are the most common. Sometimes electric fans are used in conjunction with an engine-driven clutch fan (typically, an electric pusher fan mounted ahead of the rad). This arrangement is particularly useful if heavy cooling tasks are mandated by the application (a good example is a pickup truck with a factory towing package). This might be a good choice for a Corvette that's either blessed with a cooling dilemma or one that sees double duty as a weekend racer.
So which fan is best for your Corvette? It all depends upon the application and the room you have to work with. If you have the room, a Detroit-style engine-driven clutch fan with a full shroud is most certainly a good bet. Another really good arrangement is a dual electric puller system, complete with an integral shroud (as shown in the accompanying photos). The worst possible arrangement is an inexpensive discount store flex fan without a shroud or a single pusher electric without a shroud (with these setups, you're only asking for trouble). All of the other combinations fall somewhere in between.
When all is said and done, there is one major point to keep in mind: There is virtually no way to "over cool" your Corvette. And the more power your engine produces, the more cooling capacity you'll need. Just some food for thought.