The quest for enough horsepower is a frustrating one. It seems like no matter how much you get, you just end up wanting more. The desire to have more ponies generally leads to bigger cams, higher-flowing heads, and a host of other upgrades. The only problem is this extra power comes at a big cost. Maybe you get less gas mileage, or a cam becomes so lopey, it's troublesome on the street. Enter nitrous oxide: the magical combination of atoms that lets the user run a relatively mild engine and still put down serious power with just the flip of a switch.
Nitrous oxide works by introducing extra oxygen into the intake charge, which allows more fuel to be added and converted into energy. This can greatly increase the power produced by the engine. Another benefit is that evaporation in the intake manifold helps drop the intake charge temperature, since nitrous oxide is stored as a high-pressure liquid. This evaporative cooling causes a denser charge, and can increase power output, as well as reduce detonation.
But like everything in life that sounds perfect, there's a price-and this time it's vigilance. When using nitrous, you have to be careful with bottle pressure, fuel pressure, ignition timing, and other factors. If all is set up properly, it can be a beautiful thing; if not, disaster looms.
We wanted to see how a basic nitrous system could up the power on an average engine. Our test mule was a '66 Nova, with a fairly sedate 350 small-block engine. For a system, we chose Zex's new perimeter plate setup, whose innovative design caught our attention. The Zex system is known as a perimeter plate, meaning that the nitrous and enriching fuel are introduced into the plenum below the carb through a series of small, evenly spaced holes. This reduces-or in some cases eliminates-the uneven distribution encountered with other systems.
The owner of our test Nova, Scott Miller, wanted to know if he should switch his dual-plane intake to a single-plane, so we called up Zex to ask. Zex's Matt Patrick tells us, "Our perimeter injection plate is ideal for use with dual-plane intake manifolds. Traditional spray-bar-type plates have difficulty with proper distribution, due to the center divider being placed directly under the spray bar. Since the injection spray with the perimeter plate occurs around the outer edge of the manifold plenum, distribution of the nitrous and fuel is excellent. In fact, our dyno tests proved that the perimeter injection design actually decreased the engine's normal cylinder-to-cylinder mixture variations." With that bit of information, we were ready to start the install. And after that, we did baseline, 100 hp, and 150 hp shot dyno pulls, and saw a peak-to-peak increase of up to 93 hp to the rear wheels. Check out the details of this easy weekend horsepower upgrade.
Stuff you'll need:
*Basic wrench and ratchet set
*Selection of screwdrivers
*Tubing bender for the purge line
*Extra 18-gauge wire
*A drill and various bits
*Extra zip ties
*Wire crimper
*Timing light
*Extra fuel line
| WHERE THE MONEY WENT |
| ITEM: | PART
NUMBER: | STREET
PRICE: |
| Zex Nitrous System: | 82040 | $544.99 |
| Zex Purge Kit: | 82010 | $109.95 |
| Zex Bottle Heater: | 82006 | $101.00 |
| Zex Bottle Gauge: | 85005 | $43.95 |
| TOTAL: | $799.89 |
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 This Zex nitrous kit includes...  This Zex nitrous kit includes everything you need for a basic nitrous install: bottle, valve, longer carb studs, braided lines, solenoids, brackets, gaskets, switches, wire, perimeter plate, and enough hardware to get it all working (PN 82040). |
 Two items that can help you...  Two items that can help you get the most out of your nitrous system are a bottle heater and a purge kit. The heater helps increase bottle pressure and maintain the optimal range of 900 to 1,000 psi (PN 82006, $101). The purge kit makes it easier to deliver a pure, cool nitrous hit when you engage the system (PN 82010, $109.95). |
 The heart of the Zex system...  The heart of the Zex system is this perimeter plate. It fits any square flange, 4150-style carburetor-equipped engine, and is different from traditional spray bar plates. Around the perimeter of the plate is an arrangement of 12 injection points, which provides a more even distribution of the nitrous oxide and fuel, resulting in more power. In addition, since the chilled nitrous travels through the plate, it drops overall charge temperatures during use. The plate is tunable for a 100- to 300-hp shot. |
 This is our starting point:...  This is our starting point: a typical 350 small-block Chevy engine. It has a stock rotating assembly, Keith Black Hypereutectic pistons, 10:1 compression, an Edelbrock Performer dual-plane intake, and a Holley 750 carb. |
 We removed the Holley, and...  We removed the Holley, and then installed the Zex plate using the supplied gaskets. According to Zex, this system is ideal for a dual-plane intake like the one on our Nova's engine, since it supplies nitrous and fuel more evenly than a spray bar system. |
 Our car had a trans kickdown...  Our car had a trans kickdown plate between the carb and the intake manifold. This plate was reinstalled above the Zex plate to keep clear of the spray pattern, so we had to reuse one of the original gaskets. |
 Next, we mounted the fuel...  Next, we mounted the fuel and nitrous solenoids to the supplied brackets, and attached them to the carb studs. We then installed the jets. Though the Zex plate is fundamentally different from other systems, changing the jets is done the same way. Initially, we set up the plate for a 100 shot, per the Zex-supplied chart. |
 We mounted the solenoid activation...  We mounted the solenoid activation switch to the bracket, and set it up so that the system would only trigger at wide-open throttle. It took some work to get the switch in just the right spot, but the bracket is designed to be easily bent into the correct position. |
ZEX On The Dyno
The plan was to make a couple of baseline pulls, then to try pulls with the 100hp and 150hp jets. The 10:1 350 was running 91-octane gas, so even the 150 shot was pushing it a bit. The base runs were done at 38 degrees of total timing. For the nitrous, Miller retarded the timing 4 degrees for the 100 shot, and another 2 degrees for the 150 shot. We ended up making an additional 59 hp (peak-to-peak), and 85 ft-lbs of torque with the 100 shot. Then we moved up to the 150hp jets, and saw 93 hp and 164 lb-ft over the naturally aspirated baseline. (That's a gain of over 70 percent in rear-wheel torque.) On the last run, we picked up a tiny bit of detonation, so Miller will bump up the octane with racing gas when he hits the track.
Dyno Runs-Rear-Wheel PowerBaseline (corrected), 38 degrees timing
211 hp at 5,012 rpm, 230 lb-ft torque at 4,251 rpm
100 Shot (corrected), 34 degrees timing
270 hp at 5,264 rpm, 315 lb-ft torque at 4,046 rpm
150 Shot (corrected), 32 degrees timing
304 hp at 5,060 rpm, 394 lb-ft torque at 3,899 rpm
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 Finding a good spot to mount...  Finding a good spot to mount the nitrous purge solenoid was sort of a pain. It needs to be away from heat, but close enough to be able to see. (When purged of air and ambient-temp nitrous, the stream changes from clear to a white fog, which is how you know the system is properly purged.) We picked the cowl area, and only had to drill one tiny hole in the rear cowl panel. The two wires from the purge solenoid were then run to the interior, so they could be wired into the supplied momentary switch and a 12-volt power source. |  Inside the car, we followed...  Inside the car, we followed the detailed wiring instructions supplied by Zex, and made all of the electrical connections. The Nova's owner, Scott Miller, also owns a sign shop, so we were able to fab this switch panel out of scrap aluminum. We wired the heater so it would only work with the ignition on. This is slightly inconvenient, but at least he won't have to worry about killing his battery if the switch is accidentally left on. |  Here's the installed assembly....  Here's the installed assembly. The heater has a built-in thermostat to help maintain optimum bottle pressure, and all the electrical components, such as the relay, are molded into the heater. The bottle heater wires run under the car and into the interior, where they are attached to the supplied switch; the nitrous line runs under the car to the front of the engine bay. Helpful Zex included more than enough wire and braided line to route the system on our Nova. |
 After installing the system,...  After installing the system, we realized we didn't have a nitrous pressure gauge, so we ran down to our local speed shop for a Zex gauge (PN 82005, $43.95). Since bottle pressure is so critical, we didn't consider this an option. Get a gauge of some sort. |  We then moved to the trunk...  We then moved to the trunk to mount the bottle. The easiest way is putting the brackets on the bottle, setting it in place, and marking the holes. You'll also need a hole for the nitrous line to exit the trunk, as well as a hole for the wires that feed the bottle heater. |  Originally, we had the two...  Originally, we had the two Zex solenoids mounted to the carburetor, but found they got in the way of the air cleaner. After trial and error, we mounted solenoids to the valve covers, and the wires were then connected to the system as shown in Zex's diagram. |
 |  Here's the engine after the...  Here's the engine after the install. Miller decided to ditch the old points-style distributor in favor of an MSD and new plug wires. With the system installed and tuned, it was time to hit the Mustang chassis dyno in the Primedia Tech Center. |  |