Adding 171 Dyno-Proven Horsepower With Zex Nitrous

If Street Outlaws and the Fast and the Furious franchise are any indication, nitrous oxide is as popular as ever — and for good reason. Nitrous oxide has a lot going for it, including significant power gains, low cost, and ease of installation. Let’s not forget how easy it is to conceal, for those looking for the ultimate in performance deception.

Initially used as both an anesthetic and as a performance enhancement for British and German World War II aircraft, it eventually trickled down to hot rodders and racers looking for the ultimate bang for the buck. If someone ever writes the quintessential book, titled Cheating to Win, rest assured it should contain at least a full chapter on nitrous oxide.

It is amazing what a difference this simple, little purple plate makes to the performance of your Ford. The Zex Permimeter Plate nitrous system really woke up our 347-stroker small-block.

Nitrous oxide has been present (if not always visible) at the top levels of drag racing, NASCAR and even the Brickyard. That’s right folks; more than one, down-on-power team at the Indy 500 relied on a little boost in a bottle to qualify for the show.

Though chock full of serious potential, nitrous oxide is chemically similar to the air we breathe. It only lacks the more stable oxygen molecule (N2O versus N2O2). The key to power potential of nitrous oxide is actually the oxygen contained in that compound.

Based on a late-model 5.0-liter block, our 347 featured a forged rotating assembly, including a 3.40-inch stroker crank and a set of 5.40-inch connecting rods from Speedmaster. These were combined with a set of JE forged pistons and Total Seal Rings. We also added a Comp XFI cam and CNC-ported, ProMaxx aluminum heads.

One common misconception about nitrous oxide, perpetuated by both TV and the movies, is that it is both flammable and explosive in nature. The truth is that touching a match (or even torch) to the chilly stream of nitrous oxide will result in said fire being simply, and easily, extinguished. Despite the depictions, there will be no huge explosions and no fireballs – not even so much as a flickering flame. The special effects teams get all the credit for exploding cars, albeit improper heating or damage to the pressurized bottle can certainly create havoc.

Nitrous Science

Chemically speaking, the oxygen in the compound is certainly flammable, but the compound itself is not. It is only when the oxygen molecules are liberated from the compound that they can be used in conjunction with fuel to produce extra power. To release the oxygen molecules from the compound, the nitrous oxide must first be heated to 572 degrees (in the combustion chamber).

The ported heads and healthy Comp XFI cam were fed by a single-plane Edelbrock Victor Jr. intake. Controlling the air and fuel to our test motor was a Holley 650 Ultra XP carburetor. To ensure the nitrous combo had plenty of spark energy, we installed this MSD billet distributor and a 6AL ignition amplifier. Run on the dyno with Hooker headers, a Meziere electric water pump and Speedmaster neutral damper, the 347 produced 441 horsepower at 6,500 rpm and 405 lb-ft of torque at 5,000 rpm.

As if the extra power wasn’t enough, the compound also offers a side benefit in the form of charge cooling.

Technically, nitrous oxide is not a fuel, but rather an oxidizing agent. Once released, the free oxygen molecules work to support (or enhance) the combustion process. This process requires burning some other fuel, like gasoline or methanol. As if the extra power wasn’t enough, the compound also offers a side benefit in the form of charge cooling.

Nitrous is stored as a liquid, and when injected, it is converted into a gas. This process is called boiling, though it occurs with nitrous oxide at a chilly -129 degrees. The conversion from a liquid to a gas absorbs a great deal of heat from the surrounding area, to say nothing of the added benefit of the introduction of a compound at -129 degrees to your inlet tract.

Power Potential

Given the short science lesson, it should come as no surprise that the combination of extra oxygen molecules and additional cooling produces some pretty impressive power gains. Every bit as important for our requirements is the fact that the power potential of nitrous oxide was independent of the power output of the motor we applied it to.

After running the 347 in naturally aspirated trim, we yanked the Holley carb and installed these longer mounting studs. Next, we installed the Zex Perimeter Plate nitrous system. The solenoids were mounted on a Wilson nitrous mounting plate (not part of the kit) on loan from Westech. The Perimeter Plate features 12 dispersion holes which equally distribute the nitrous and fuel into the intake manifold.

Rather than build some high-strung, unreliable race motor, we simply built a decent little Ford stroker, then added some nitrous.

Rather than build some high-strung, unreliable race motor, we simply built a decent little Ford stroker, then added some nitrous. Nitrous oxide is not picky, and can be added to just about any combination, from mild to wild with amazing results. We mentioned that the nitrous oxide was responsible for cooling the inlet charge, something that both improves power and helps suppress detonation.

As with all builds, the power gains and life expectancy of the motor are directly related to the tune, or lack thereof. Naturally, the proper air/fuel mixture and (especially) ignition timing are critical on a powerful nitrous motor, though we got a little aggressive on the tune of our 347 with excellent results. Applied and tuned properly, a modern nitrous system, like our Zex Perimeter Plate, can provide safe, effective and reliable power gains.

Stout Stroker

To demonstrate just how easy it is to produce serious power from a streetable stroker combination using nitrous oxide, we first assembled a small-block Ford test engine. Our goal was to build a healthy combination that could be subjected to years of daily driving while continuing to offer super-car levels of performance. To make more power, we started the build with more motor.

Rather than chose a stock-displacement 5.0-liter, we stepped up to a 347 stroker. After boring the production block .030 over, we installed a 4340 forged, 3.40-inch, stroker crank and 5.40-inch forged rods from Speedmaster. These were combined with forged flat-top pistons from JE. Completing the short-block assembly was an XFI236HR cam. The Comp grind featured .579-inch lift, a 236/248-degree duration split and 114-degree lobe separation. Also included in the short block was a set of drop-in, hydraulic-roller lifters, a double-roller timing chain and hardened pushrods all from Comp Cams.

The Zex kit included a pair of solenoids to supply nitrous and fuel to the plate. The power output supplied by the Zex Perimeter Plate kit was adjustable using the supplied nitrous and fuel jets. Our kit was adjustable from 100-300 hp, but we started small with a 100-hp shot.

The increased displacement required additional airflow, so we topped the 347 with a set of ProMaxx aluminum cylinder heads. These 210cc heads featured full CNC porting to unleash peak intake flow numbers exceeding 320 cfm. They also feature 60cc combustion chambers, a 2.08/1.60 stainless steel valve package and were completed with a dual-spring package from Comp Cams.

The heads were capable of supporting over 650 horsepower in naturally aspirated trim, so they were more than adequate for the power potential of our street/strip 347. Completing the top end was an Edelbrock Victor Jr. intake, Holley 650 Ultra XP carb and MSD distributor. Additional touches in the build included ARP hardware, Fel-Pro gaskets, and Comp 1.6-ratio Gold roller rockers. Covering the roller rockers and hardened pushrods, and upping the bling factor was a set of Speedmaster cast-aluminum valve covers.

Perimeter of Power

To provide that boost in a bottle to our stroker, we selected a Zex Perimeter Plate nitrous system (PN 82040). Designed to be sandwiched between the carburetor and intake, the Perimeter Plate did not rely on spray bars, but rather 12 unique, equally spaced injection points. Each orifice was designed to evenly distribute nitrous and fuel to the intake manifold to maximize safe power production.

Running the 100-horsepower jetting, the sprayed 347 produced 569 horsepower and 519 lb-ft of torque. After stepping up our jetting to the 150-horsepower level, the nitrous stroker produced 612 horsepower and 574 lb-ft of torque.

Dyno Results

The combination of our ProMaxx-headed 347 stroker and Zex Perimeter Plate nitrous produced serious results. Run in naturally aspirated trim, the 347 stroker produced 441 horsepower and 405 lb-ft of torque. After installation of the Zex nitrous kit (with 100-horse jetting), the peak numbers jumped to 569 horsepower and 519 lb-ft of torque. Thanks to aggressive tuning (12.3:1 air/fuel and just two-degrees of timing retard), the 100-horse jetting increased the power output by 128 horsepower and 114 lb-ft of torque.  

If a little nitrous is good, then more must be even better, right? The great thing about a nitrous kit is the ability to easily increase the power gains. Stepping up to 150-hp jetting produced peak numbers of 612 hp and 574 lb-ft of torque. In keeping with the 100-horse jetting, the 150-horse setup increased the power output by 171 hp and 169 lb-ft of torque. Proper tuning is critical on nitrous and you can get more aggressive with higher fuel octane.

Even distribution of fuel and nitrous is critical for safe operation. The last thing you want is one cylinder running with too much nitrous and not enough fuel. It also equalizes the power production from all cylinders. Using the supplied jetting, the Perimeter Plate system was adjustable from 100 to 300 horsepower. For our test, we selected jetting to first provide 100 horsepower, but then stepped this up to 150 horsepower. The ability to easily increase the power output is one of the best facets of nitrous. Gains of 50, 100 or even 150 horsepower are just a jet change away.

To properly test the Zex Perimeter Plate, we established a baseline by running the 347 stroker on the dyno in naturally aspirated form. After dialing in the air/fuel and timing, the ProMaxx-headed 347 produced 441 horsepower and 405 lb-ft of torque. Even without the nitrous, the carbureted stroker was plenty healthy, given a stock 5.0-liter will produce just 255 horsepower under the same conditions. After establishing our baseline with the 347, we quickly installed the Zex Perimeter Plate nitrous kit. Using .046 nitrous and .043 fuel jetting to supply an extra 100 horsepower, we were rewarded with peak numbers of 569 horsepower and 519 lb-ft of torque.

Credit the extra power to our choice to retard timing only two degrees and run the air/fuel mixture at 12.3:1. Stepping up in jetting to a .062 nitrous and .053 fuel for 150 horsepower, the nitrous-injected 347 topped the 600-horse mark with peak numbers of 612 horsepower and 574 lb-ft of torque. Our aggressive tuned combo delivered gains of 171 horsepower and 169 lb-ft of torque with the 150-horse jetting, but even with a milder state of tune, the Zex Perimeter Plate provided plenty of extra power.

Using the Westech heater, we dialed up the bottle temperature to ensure adequate nitrous pressure. The dyno featured a separate fuel system to feed the nitrous. We dialed in this system’s fuel pressure slightly lower (and leaner) than the recommended (and safe) 6 psi.

Given our results, it’s safe to say a properly tuned nitrous kit can take a small-block Ford to another level of performance. For more on the Zex Perimeter Plate system, you can check out company’s official site here.

Article Sources

About the author

Richard Holdener

Richard Holdener is a technical editor with over 25 years of hands-on experience in the automotive industry. Despite receiving a Bachelor of Arts in Advertising, Richard decided to follow his passion for all things automotive. Early on, he decided to specialize in direct back-to-back dyno testing everything from simple throttle bodies and air intakes to supercharged strokers and the various forms of forced induction. Along with the technical articles, Richard has written no less than 10 different performance books. The titles include back-to-back dyno testing on the early 5.0-liter Ford, Modular Ford and both LS1-LS6 and LS3-LS7. Additional titles covered Honda B&D-series performance, Honda K-series performance and even a book on the Ford Focus (Richard is fluent in both Import and Domestic Performance). Not content to simply stand behind the camera, this hands-on approach has resulted in a finalist positions in Engine Masters, national road race championships and land-speed competitions, as well as membership into the exclusive 200-mph club.
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