Are Superchargers direct bolt on kits?

The answer is yes, however there are a lot of things between the lines that people don't know. Educate yourself and ask questions.  Research and do your homework.  The best thing to do is get a game plan together and plan out what you want to achieve.  For people that can not do their own work, the best thing to do is develop a relationship with a reputable speed shop that can do the work for you. Let them know your intentions and plans. The reason for this isn't so that they will hopefully give you a better price discount on the kit, but to be there for you after the sale for technical support. Sooner or later you will need them, so it might be best to spend a few extra dollars with a top notch installer, instead of trying to get the kit for the best price and trying to get the best price on the install. 

What should I known before I purchase a blower.

A blower is a large investment for everyone. Educate yourself as much as you can with the inner works of a supercharger system and the preventative maintenance you need to perform. You have to be mentally and financially prepared for any mishap or mechanical failure down the road.  You have to learn that you just can't turn the key, routine maintenance is important. So don't go out and purchase a supercharger kit if you don't have the financial means to repair any possible engine damage that may occur. It's also a great idea to do a leak down and or compression check on your engine before you start.  This tells you if anything is wrong before you start your installation. This will also serve as a reference done the line as part of any preventative maintenance. 

Terminology every supercharger owner should become familiar with:

Detonation - Detonation (also called "spark knock") is an erratic form of combustion that can cause head gasket failure as well as other engine damage (Piston ring lands). Detonation occurs when excessive heat and pressure in the combustion chamber cause the air/fuel mixture to auto ignite.  The hammer like shock waves created by detonation subject the head gasket, piston, rings, spark plug and rod bearings to severe overloading. Mild or occasional detonation can occur in almost any engine and usually causes no harm especially running naturally aspirated (no power adder). But detonation in a power adder application where the cylinder temps are high to begin with can cause engine failure. So if you hear knocking or pinging when accelerating or lugging your engine, you probably have a detonation problem. Unfortunately most damage is already done by the time its heard, and detonation can be so slight that you might not hear it. 

Preignition - Another condition that is sometimes confused with detonation. This occurs when a point within the 
combustion chamber becomes so hot that it becomes a source of ignition and causes the fuel to ignite before the spark plug fires. This, in turn, may contribute to or cause a detonation problem. Instead of the fuel igniting at the right instant to give the crankshaft a smooth kick in the right direction, the fuel ignites prematurely (early) causing a momentarily backlash as the piston tries to turn the crank in the wrong direction. This can be very damaging because of the stresses it creates. It can also localize heat to such an extent that it can partially melt or burn a hole through the top of a piston! 

Air to fuel ratio  (a/f ratio for short) This is a measure of (mass of Air) & (mass of Fuel) or the percentage of fuel left in the exhaust gas. This ratio is a number commonly thrown around when talking about fuel usage and economy. It refers to the optimal ratio of air to fuel--11.9:1 air to fuel. That is to say, for every 11.9 parts of air, there is one part of fuel, measured by mass and not by volume. The higher the numeric number the leaner the car is. The lower the number, the richer the car is.  Richer is better from a safety standpoint. The leaner the numeric number from 11.9:1 the more of a chance to hurt engine parts. 

To measure the air/fuel ratio, an oxygen sensor is placed in the exhaust stream.  After sampling the gases, the sensor sends back a voltage reading to the computer that is interpreted to calculate the air/fuel ratio. There are different types of oxygen sensors, but most of those used in modern cars, and by aftermarket gauges, are of the four-wire heated variety. These provide faster and more accurate readings, as they do not rely on the exhaust gases to bring them to operating temperature.  Some gauges will simply tap into the Factory 02 sensor. This is wrong to do! Factory 02 sensors are not accurate at WOT a/f ratios. 

EGT aka Exhaust Gas Temperature - This measurement is closely related to a/f ratio. Supercharged applications should see an maximum EGT of 1400 degrees. The higher the number the leaner the car, the lower the number the richer the car. Dyno tuners tend to target for a EGT of 1200-1250 because a car will run leaner on the street or track than it will on the dyno. A nice safe number to see on the street is 1300. 

How do you measure EGT's? With a meter and a probe. The probe is mounted 1" away from the exhaust port flange by the cylinder head.  EGT meters can be permanently mounted and are very durable. They almost never go bad. 

What are the pitfalls of a supercharger. 

Heat and detonation are the main concerns. Because the supercharger is dissipating a lot more heat in the engine compartment, you have to make sure your cooling system is up to the task. I recommend a fan switch at the very minimum, and keep it on all the time. This generally helps keep your temperature down. You want to make sure the temperature stays under 200 and as close to 180 as possible. Another good idea is to get a better radiator. The stock radiators are very pitiful. In the 4.6 modular cars they use a 1 core radiator from the factory. This isn't going to get the
job done. 

Once your cooling system is up to the task, make sure you give your car the gasoline it needs now. At the very minimum, 93 octane should be used. 94 Octane is better, and 94 octane with a can of 104 octane is the best preventative maintenance you can do for your car. 

Stock flexible inlet tubings are terrible. They can rip and tear very easily. This can cause unmetered mass air into the air tract and cause your car to run very lean. The best preventative maintenance I recommend purchasing a power pipe to replace any flexible plastic tubing.  On the 4.6 cobras, the stock plastic tubings can deform with  a good amount of heat. This can also cause big enough vacuum leaks to run lean. Replace them with Aftermarket power pipes. 

It's always a great idea if you have the opportunity to put a wide band 02 sensor on your vehicle and monitor the air to fuel ratio. The air to fuel or a/f ratio is the measurement of how lean or how rich your car is running. It is a major component to your car not breaking engine parts. Some kits such as the 4.6 Mustangs come with a computer chip equipped. Some chips have been known to run too lean. It's always a great idea to at least verify your a/f ratio with a wide band o2 sensor on a chassis dyno. If you don't have access to a chassis dyno, purchase an Exhaust Gas Temperature meter.  If you have access to a very reputable tuner that can burn his own chip, have a custom chip burned to your specific cars needs. Not every car is the same, even if it is the same car with the same combination. Nothing can beat a custom burned chip from a reputable tuner.

Are intercoolers necessary?

Not on a stock kit. Paxton, Vortech, ATI, Powerdyne, Kenne Bell all design their kits carefully. An intercooler will reduce the chance of detonation by reducing the inlet air temperature going into any engine. However, intercoolers are more important for applications where a supercharger is being spun hard and out of its efficiency range.  A stock kit with a stock pulley can not simulate these conditions. Intercoolers are great when you want to run a more aggressive calibration in the tuneup. By reducing discharge temperatures by 75-100 degrees, you can safely add more timing without detonation. More timing means more power. 
But is it necessary? Absolutely not. 

Quick Preventative Maintenance guide 

1. "Read" your spark plugs. The wrong heat range plug can cause detonation as well as preignition. If the insulators 
around the electrodes on your plugs appear yellowish or blistered, they may be too hot for the application. Another sign of detonation is black specs (aka pepper) on the ceramic portion of the plug. Try the next heat range colder spark plug. I recommend Autolite 764's or NGK TR6's for stock kits. 
2. Make sure the cooling system is efficient (Fan switch, better radiator). 
3. Run the proper gasoline you need. Make sure the gasoline is fresh, and try to have your tank empty if you store your car. 
4. Inspect your supercharger tubing for cracks and tears. Invest in some good quality aftermarket parts. 
5. Verify your air to fuel ratio with an a/f meter or EGT gauge. 
6. Perform a compression check before the supercharger install and perform one every 6 months to verify all internal engine parts are working properly. Chart and log your results for future reference. 
7. Change your oil and filter regularly I recommend every 1500-2000 miles. . 
8. Maintain a clean air filter. 
9. Make sure all fluids are up to operating temperature before you start running the car hard. 
10. Check the condition of the supercharger belt. Replace as needed.

Dave King