We just got the results back from our latest reader survey (hey, don't ask us why it took a year), and they confirm something we already knew: Nitrous oxide is the Car Craft reader's favorite power adder. Maybe it's the low initial buy-in, the undisputed bang-for-the-buck potential, or the simplicity of flipping a switch for an extra couple hundred horses. Whatever the reason, nitrous oxide topped the list of choices, easily eclipsing blowers and turbos in popularity.
We hate to give any credit here, but the success of the bafflingly popular movie The Fast and the Furious has driven sales of "noss" through the roof. That's been a good thing for everybody who makes nitrous kits, because the huge profits they reap from fools who want to blow the intake welds on their Hondas means more cash in the coffers to develop and market high-quality, low-cost plate and fogger systems for real musclecars like ours. So there. Now you've got at least one positive thing to say about the import scene.
There are many types of nitrous systems to choose from, ranging from inexpensive plate systems to megabuck fogger-style systems that look like miniature oil refineries mounted to the top of an engine. Plate systems, which mount between the intake manifold and carburetor like a spacer, are definitely the easiest to install, because all you have to do is lift the carburetor, mount the plate, and bolt the carb back on. Run a few fuel and nitrous lines, mount the bottle, and crimp a few wires, and you're done--easy extra horsepower. In the case of Wilson Manifolds' Nitrous Pro-Flow plate nitrous systems, the work is really easy, thanks to the unique solenoid mounting plate that comes with the solenoids, wiring, and spray-bar plate pre-assembled. It's relatively pricey, but it's also a work of art, and definitely worth the cost if you want a state-of-the-art setup.
We've had this particular system for quite some time. In fact, we've been intending to install it on our '86 Mustang project car for over a year now (hey, we've been busy compiling the results of our reader survey), but we finally couldn't wait any longer and bolted it onto a small-block Chevy we had at our dyno shop to see how it worked. The test engine, which we chronicled in "530 hp From Spare Parts" (Dec. '02) is equipped with Edelbrock E-Tec 200 aluminum cylinder heads, a rumpity Lunati solid flat-tappet camshaft (254/259 degrees duration at 0.050 and 0.562/0.561-inch lift), and a stout bottom-end consisting of Probe forged pistons, Probe 6-inch forged I-beam rods, and a GM forged crankshaft. We knew it could take a stout hit of laughing gas, and the smallest set of jets in the Wilson system, which is adjustable from 175 to 350 hp, looked like a good place to start.
All it took was one pull to find the answer we were looking for. We poured in some good gas (Wilson recommends race gas for any engine running more than 9.0:1 compression; our 350 has 11.25:1 so we ran Union 76 114-octane leaded racing fuel), dialed back the timing 10 degrees from 36 to 26 total degrees (Wilson recommends retarding timing about 3 degrees for every 50 hp of nitrous), cracked open the bottle valve, and whacked the throttle to wide-open. At about 4,000 rpm, we manually hit the nitrous button and cackled as the engine practically leaped off the dyno stand. The results were impressive: 706 hp at 6,300 rpm and 637 lb-ft of torque at 5,500.
We still had a handful of jets that could have taken us to even greater heights--750, 800, maybe more. But why get greedy?
The Fuel System
Whenever we talk about power adders, it's important to also discuss the fuel delivery system, because all that extra power needs a reliable source of fuel to feed it. With nitrous systems, this is important for two reasons. First, since the ratio of gaseous nitrous to the enrichment fuel is a critical part of the "tuneup," the volume and pressure of fuel delivered to the fuel solenoid must be accurate and controllable. If there's too much enrichment fuel, the mixture is rich or "fat," and you'll lose power. If the mixture is too lean, you can get into big trouble with detonation or a backfire, which is the biggest cause of broken parts when using nitrous.
A good fuel system not only ensures adequate delivery of fuel, it also allows you to fine-tune the nitrous system by independently regulating the fuel pressure. Wilson recommends setting the flowing fuel pressure to the fuel solenoid between 7.5 psi for race gas and 8.5 to 9 psi for pump gas, with higher pressure being on the safer rich side and lower pressure leaning to the lean side. Ideally, the nitrous system should be plumbed so you can regulate fuel pressure to the solenoid independently from the fuel pressure to the carburetor. Depending on your setup, the best way to do this may be to run a separate pump and regulator to the nitrous system from the fuel tank.
Nitrous: It's the perfect weapon for those with a greedy need for speed. Wilson Manifolds' Nitrous Pro-Flow systems aren't the cheapest you can buy, but in our opinion, they are among the finest, built with attention to detail that reaches to the level of artistic perfection.
We don't recommend using nitrous plate systems with dual-plane intake manifolds unless you're using a very mild shot, because the divided plenum can interfere with the distribution from the nitrous plate. We certainly wouldn't use a dual-plane with even the minimum 175hp jetting provided with the Wilson system, so we equipped our test engine with an Edelbrock Super Victor, which is the only currently available single-plane intake for the Vortec-pattern Edelbrock E-Tec 200 heads. Naturally aspirated power with this combination was actually down a few horsepower, but we'll make up for it in no time.
Wilson's patented single-spray-bar plate incorporates a unique pattern of orifices designed to optimize the distribution of nitrous and fuel into the plenum.
Nitrous Pro-Flow plate systems are available with patented burst panels built into the manifold spacer. These unique panels are designed to act as relief valves in case of a nitrous backfire, which can wreak havoc on an engine, especially if the carb throttle plates are partially closed. We've seen backfires so bad they've blown hoods and even carburetors off cars. The panels are easily and cheaply replaced in case of a bad burp.
Ideally, the nitrous gas and the enrichment fuel instantly mix together in the proper ratio to ensure that the system works to its full potential. If pressurized nitrous leaks out of the system and causes a pocket of air to develop in the line, there could be a lag when the solenoids are activated while the gas flows through the lines and solenoid and into the engine. If fuel enters the manifold before it's mixed with gas, the mixture will be overly rich and down on power. To avoid this, a purge solenoid (arrow) allows you to prime the system and remove any air, which ensures the nitrous will be ready to go at the plate when the pass begins. A hard line is run from the purge solenoid usually to the cowl area to vent the excess gas.
A carburetor-mounted wide-open-throttle activation switch is one of the most foolproof ways to activate a nitrous system. It's more accurate than using a handheld button, and it can be wired through a relay to a transbrake or a progressive timer for consistent, repeatable results. Wilson makes these convenient brackets to mount the switch to Holley and Demon-brand carbs.
Unlike any other nitrous system we've ever seen, the Nitrous Pro-Flow kit comes with the fuel, nitrous, and purge solenoids prewired into a Weatherpack-style harness. A complete wiring diagram is included, along with a relay to power the system. Very trick, but you will need a pair of Weatherpack crimping pliers to make the proper connections. | 
The Nitrous Pro Flow system is completed with a bottle and line kit, plus an optional blow-down tube that vents gas out of the passenger compartment in the case of a ruptured valve. These are usually required by any racing organization if the bottle is mounted inside the car. The system also includes a bottle filter that prevents any impurities from clogging the solenoids, and a pressure gauge to monitor bottle pressure, which should be in the 950- to 1,000-psi range for best results. |
During the test we ran Autolite 3923 copper resistor plugs, which are one stage colder than the 3924s we normally use in naturally aspirated engines. The colder the plug, the more it resists heat buildup at the tip of the electrode, thus decreasing the chance of detonation in a nitrous or supercharged application. The projected tip design of these plugs, which aids fuel efficiency, often causes problems with nitrous because the relatively long electrode hangs out into the chamber and has a tendency to act like a glow plug. Close inspection revealed a bluish tint on the tip of the 3923s--anindication that we needed an even colder plug, like a 3922. | 
Dyno Results |