Question #1-How much can I use?
As much as you want until you blow the head gaskets out of it, I would not use more than a 50HP or 75HP shot until you know what your doing. The critical part is the solenoids and the fuel pump, both have to flow large amounts of N2O and fuel and must be in top shape so you don't starve the engine of either at full load (kiss it goodbye). Use the largest most expensive fuel pump you can afford and use a pressure relief plumbed into the fuel return line to maintain your pressure, I can't stress this enough. Big fuel lines (1/2" at least) right from the tank (inside the tank too!) insulated N2O lines right to the carb (you do not want the stuff vaporizing before the nozzles). Once you have the entire system established and working properly with the smallest "pill", you can try the larger "pills". Put a gauge on every thing leading to the engine, oil pressure, fuel pressure, N2O pressure etc. The last thing you want is the fuel pressure dropping, the N2O pressure rising because it's hot outside and your oil pressure dropping at the same time (kiss it goodbye). Personally I like the bottle mounted in the front clip somewhere so the line length is kept to a minimum. A key point to remember is if one gauge is dropping or low, shut it down-it's not worth it even if you have to swallow some pride and lose a race.
Question #2-Is it hard to install?
To do it right means reengineering your entire fuel system and intake distribution if you want that 150HP shot. Ideally your engine should have forged pistons fitted on the loose side in case you detonate the motor at full load with a bottle that suddenly runs dry, freezes up a solenoid or any other million things that can go wrong. If you have cast or eutectic pistons and you detonate at full load-kiss it goodbye. In my opinion there no is half way to build a nitrous motor, sure there are many guys just buying the kit and doing it half-a__ed but they will get bit eventually. Seen it happen a million times. Another real important point is your HEI is basically useless at the kinds of cylinder pressures N2O can generate-think FRANKENSTEIN!
Question #3-Where do I get my bottle filled?
The local rod shop, medical gas suppliers, welding gas suppliers sometimes. Best to phone around and make sure your bottles are getting weighed while it is being filled. You should be paying by the pound not by the bottle. One last thing, buy the biggest bottle you can afford/fit it's the s_its having to refill every week and don't use it if you only have a quarter bottle left-refill!!
Message edited to be chemically correct
[ March 22, 2002: Message edited by: 4 Jaw Chuck ]</p>
“She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself.”
— Han Solo