Q-Jets are indeed the most sensitive carb there ever was, save for perhaps a Lucas, diff is the Q-Jet is likely the most EFFECTIVE and by far the most efficient carb, its hard to get closer than a Q-Jet to EFI or MFI without actually having same, its reputation as a failed carb is wholely undeserved, used within its intended operational envelope its among the best and comes in standard sizes as large as 835CFM. Remewber that the Thermo-Quad, The AVS( which is what the Edelbrock series carbs are with an Edelebrock name plate on em), The Q-Jet are ALL Carter Carburetors. When Carter no longer had manufacturers contracts for Carb they sold PRODUCTION/Distribution and sales rights to Edelbrock and others in the After market.
AS a general rule NO carb much cares for more than 6psi @ WOT, however, in good shape u can get reasonable needle n seat life at as much as 8PSI. This is fine with spray, since if ur past 6psi @ WOT ur over the recommended FP for any carbed wet plate application using spray anyway.
Nitrous and fuel jets for spray systems are calibrated based on the recommended fuel pressure for the fuel system in which they are used, if u use LESS pressure u lean up the mix and imparts a harder hit, if u use MORE u fatten up the mixture and soften the hit as well as lower the power increase u get when u engage.
Think of Turbo Chargers, Superchargers and Nitrous Oxide as 3 relatively destinct ways to achieve the same final end. To grasp this, realize that tho fuel is an accellerant it isn't the fuel that actually DRIVES the engine, it is the oxygen content of ur mixture. Of those gases included in free air, oxygen is that one which reacts the most quickly and violently to the application of heat.
The Former 2 increase the oxygen content in the combustion chamber by simply puttin more air per combustion cycle into the cylinder, Nitrous does so by introducing a mixture that is MORE oxygen laden at normal atmopheric pressures than is normal free air...
Free air under the best of circumstances, at ther most favorable atmopheric conditions is never going to exceed more than 15 per cent oxygen, usually right around 12 per cent and in cities like LA or NYC this may even get down closer to 10 per cent, Nitous Oxide on the other hand is by volume AND weight 33.333333333 per cent Oxygen in its purest form, which would b medical grade(laughing gas); commercial grade averages by supplier 30 per cent since there r other gases introduced to discourage misuse, which is what gives it its scent, medical grade is odorless and tasteless. By introducing Nitrous oxide into the incoming charge u effectively raise the oxygen content of ur charge and COOL same prior to ignition to boot since u replace a portion of the AIR the engine ingests with a more oxygen rich gas than is free air. Theoreticallly, the introduction of enough oxygen into the charge can MAXIMIZE Thermal Efficiency Potential to 100 per cent, thus allowing u to produce the max amount of power the engine is capable of producein at its size which controls the absolute amount of air the engine can move thru itself w/o boost in the inlet. With this u understand why spray is NOT equal in its power production capabilities as is a turbo or supercharger, since either of the latter can introduce more oxygen into the engine than it could possibly move under normal atmopheric pressures in the inlet by simply introducing MORE air from which to extract oxygen, while nitrous introduces more oxygen it also reduces the amount of FREE air that is ingested in each combustion cycle by replacing a replacing a reletively small amount of the free air with Nitrous OXIDE, 2 parts Nitrogen and 1 part oxygen per molecule or at the molecular structure as its known. Thus u simply can not move any more sheer volume thru an engine than its size dictates w/o pressurizing the inlet. u can maximize the amount of power capable of being produced by the amount of air volume being moved to 100 per cent but u can NOT exceed that amount, the reason u can with the super or turbo charger is cause u can MOVE MORE AIR thru the engine, both by increaseing the containment size of the inlet system and the introduction of more pressure with which to introduce same into the engine at each opening of the intake valve.
As far as use with a carb, any system u buy u buy for the type of induction system u have, simply follow all recommendations and installation instructions to the letter, buy a quality system and employ a carefull quality installation and u'll have no problems.
A note, trying to shoot more than 300bhp of spray thru an engine which employs an exhaust that is not turbo or supercharged is a wasted effort, even if u have a plate/jet system that will flow more than that, the back pressure created in ANY type of exhaust system under NA conditions will negate any gain u might get from it....
Besides, with a nitous system, u are limited to how much u can put into the engine by the number and size of the openings in the spray bars and the amount of pressure u can maintain in the bottle, any wet plate either for a carbed, EFI or MFI system is going to b maxed out by 300-350bhp. U may b able to flow as much as 600bhp or more thru a complex and dedicated FOGGER system but this only effective if the engine has that amount of power left to b produced by Max thermal efficiency; IE: u have an engine size capable of producing 1000 BHP NA and u actually make 800 of that w/o the intro of spray, u can spray all u want u'll only get another 200. The addage that there is no REPLACEMENT for displacement applies no matter how u go about power production. the larger the engine the more power its CAPABLE of producing under any circumstances u may choose to use to do so.
That is why tho spray, super and turbo chargers are indeed great substitutes for cubes, they are not a replacement and only surfice so long as the larger engine does not employ them as well.
With engine crafting for power production its important that one understand what works, how it works, where and when it works, but if u hope to do much to make the engine work better u must also understand WHY it works, if u don't understand WHY something works ur behind the 8 ball tryin to make it work better than it already does.
AS i say, spray has great advantages, but like its other 2 simular counterparts it also has DISADVANTAGES as well and thus is NOT for everyone in EVERY situation. Remeber that the best performing ride is the one that employs the best WORKING combination of factors,in THAT race; probally the most important ingrediants in same are the proficiency of the operator and the cheif wrench/builder. In fact, the greater ur proficiency in these two areas the less u need in others in order to achieve any desired end with ur ride.
My preference for spray is based on the same reason most used by those who swear its a cheat, i'de rather just make all the power i can on the mtr alone and then try to better apply that power than the guy in the other lane does with whatever amount he makes. Spray is actually NOT a power adder in that it CAN'T add any more power than the engine is capable of producing normally aspirated at PEAK thermal efficiency.
There is one other seldom considered factor in power production with ur engine, its called BRAKE FUEL CONSUMPTION, it dictates that no matter what size or type of engine u use to create any given amount of power requires the same amount of fuel consumption. U may have 2 engines producing 300bhp at some given point or other, ALL other things between these 2 engines may b diff, but at the production of 300bhp, the fuel consumption is going to b the same, tho each engine may create this amount of power at vastly diff RPM levels in vastly diff ways.
Also, no matter how u plan to achieve any amount of power from ur engine the short block must b able to contain the amount of power made w/o failure or at least w/o failure too premature, the end game is that the more power u make from ANY engine the shorter the life of same is going to b all else equal. This is proven by the fact that ANY ENGINE is going to have a shorter life the longer its held at WOT/MAX POWER PRODUCTION than will one that lives its life in moderation at some point BELOW its max power out put. More power requires more heat and friction to produce and we all know that the level of heat and friction dictates engine life more so than does any other factors.
In Effect power is actually made based on the effciency of ur inlet(Heads, valves, Valve train etc..) and exhaust, the short block simply must have sutable durability to contain same.