Compression, Intercoolers, And Water InjectionEveryone has an opinion when it comes to combining compression ratio with supercharging. Some contend that low compression with lots of boost is the way to fly, while others project that a little more squeeze is better with a blower for more power. There are no wrong answers here as long as you avoid detonation. For a street engine, a little more static compression at around 9.0:1 to 9.5:1 with single-digit boost levels and no intercooler can be made to work well with pump gas as long as you don't go crazy with timing under boost with reasonably cool inlet-air temps. High inlet-air temperature into the carburetor increases the potential for engine-killing detonation. That's why intercoolers work so well.
We all know that intercoolers work exceptionally well in reducing inlet-air temperature and therefore make more power by allowing you to run more timing before the engine detonates. They are also expensive and require significant custom plumbing that scares many enthusiasts. As an alternative, you can always increase octane by mixing race gas with pump gas, but since fuel is a consumable, paying $5.00 to $7.00 a gallon for 10 gallons of fun can become a pain in the wallet.
Another solution that reduces detonation, improves power, and doesn't cost much is water/alcohol injection. This idea is almost as old as the internal combustion engine as a cheap source of power. For supercharged engines, the idea is to use the latent heat of vaporization characteristics of both water and alcohol (ethanol or methanol) to reduce the inlet-air temperature under boost by injecting this water/alcohol mix into the engine. It's even possible to introduce this mixture into the blower inlet. This allows the mixture time to homogenize into the inlet airstream and also by vaporizing in the high inlet-air temp to reduce the temperature somewhat. Have you ever applied rubbing alcohol to your skin on a hot day? That same cooling effect also occurs in the inlet tract of a blow-through system. The oxygen content in the alcohol will contribute a small amount to increased power. Combined with the lower inlet-air temperature, this idea is a proven winner.
You could build an affordable water-injection system using a small nitrous solenoid, a high-pressure electric pump, and a jet to meter flow into the engine and trigger it with a Hobbs switch that senses when the engine sees boost. There are also several kits, including those from Snow Performance or coolingmist.com for supercharged applications for $200 and up. These companies also offer individual parts for building your own system. A slick aluminum tank partially hidden behind an inner fenderwell with a pump and a solenoid to feed a water-alcohol mix would be cool!
Plates And BracketsThe weird thing about centrifugals is that there are little companies out there making mounts for centrifugal superchargers not offered by the parent companies. As an example, while ProCharger doesn't offer mounts for small- or big-block Mopars, a company in Arizona called The Supercharger Store does. This company has built a business around making mounts for engines that take the road less traveled. They even offer a mount for ProCharger superchargers that include A/C for a 440 Mopar.
If you are building a dedicated blower motor and anticipate double-digit boost numbers, it would be beneficial to talk to your crankshaft company about a larger snout, especially for small-blocks. Beltdriven superchargers place a major load (up to 50 hp worth) on crankshaft ends, which effectively tries to rip the crank snout right off. Several companies offer big-block-snout cranks, timing gears, cam covers, and balancers for the small-block Chevy to accommodate these demands.