Why Nitrous Still Matters

Nitrous oxide remains one of the most efficient paths to significant power gains. It works across nearly any combination - stock to fully built - and delivers measurable results at the push of a button. Before examining the ZEX Perimeter Plate system and its dyno performance, a brief look at the science behind the compound provides useful context.

The Science Behind Nitrous Oxide

Nitrous oxide is an oxidizing agent, not a fuel. It will not burn or explode on its own - despite what films suggest. A motor cannot run on nitrous oxide alone. Its value lies in the oxygen molecules locked within the dinitrogen monoxide compound, which are released when heated to approximately 572 degrees during combustion. Once freed, those oxygen molecules enhance the burning of additional fuel, producing extra power.

An additional benefit comes from the phase change itself. Nitrous oxide is stored as a liquid and delivered as a gas through vaporization. With a boiling point of -129 degrees, this transition significantly reduces inlet air temperature, improving charge density and reducing the risk of detonation.

A Brief History

Nitrous oxide was first obtained by Joseph Priestley in the late 1700s and later used as an anesthetic in the early 1800s. Its application as a performance tool accelerated during World War II, when both British and German engineers sought ways to restore power lost at high altitude where oxygen is scarce. The compound supplemented mechanical supercharging systems, delivering reported gains of 600 additional horsepower on British Mosquito bombers and up to 1,000 horsepower on German JU 188 reconnaissance aircraft.

ZEX Perimeter Plate Design

The ZEX Perimeter Plate system addresses one of the most critical variables in nitrous application: cylinder-to-cylinder distribution. Unlike single wet-fogger systems used in EFI applications or spray-bar setups on carbureted engines, the Perimeter Plate uses 12 equidistant injection points to combine nitrous and fuel. This configuration is engineered to optimize atomization and ensure even distribution across all cylinders.

The plate, sandwiched between the carburetor and intake manifold, also functions as a thermal isolator. Injecting nitrous at -127 degrees through the plate cools both the intake and carburetor - a feature ZEX calls Cryo-Sync. Additionally, the high-pressure flow of nitrous and fuel through the spacer creates a low-pressure zone that enhances airflow into the engine.

The Test Engine: Dart SHP 363 Stroker

Testing the Perimeter Plate system required a motor capable of handling a serious nitrous dose. The foundation was a Dart SHP short block - a 363-cubic-inch stroker featuring splayed four-bolt main caps, a 4340-forged 3.40-inch Scat crank, matching 5.40-inch rods, and Mahle flat-top pistons. The flat-tops featured generous valve reliefs and combined with 62-cc combustion chambers to produce an 11.0:1 static compression ratio.

Cam Research Corporation supplied a solid roller profile with .736 lift (intake and exhaust), a 256/260-degree duration split, and a tight 105-degree LSA. COMP Cams provided solid roller lifters, a double roller timing chain, and Gold 1.6-ratio roller rockers.

Dart Pro 1 225 CNC heads handled airflow duties with a 2.08/1.60 valve combination, 62-cc combustion chambers, and flow rates of 325/235 cfm measured at .700 lift.

Speedmaster Parker Funnel Web Intake

The combination required a single-plane intake manifold capable of supporting the stroker's high-rpm power band. The Speedmaster Parker Funnel Web was selected for this role, paired with a Holley 950 HP carburetor. During pre-nitrous testing, the larger 950 HP carb proved worth nearly 10 hp over a smaller 750 HP unit.

The ignition system included an MSD billet distributor, Blaster coil, and Digital 7 ignition amplifier - critical for maintaining spark energy under nitrous load.

Naturally Aspirated Baseline

Before introducing nitrous, the 363 stroker was baselined on the dyno. The combination of the Dart short block, Cam Research roller cam, Dart Pro 1 heads, Speedmaster Funnel Web intake, and Holley 950 HP carb produced 563 hp at 6,700 rpm and 487 lb-ft of torque at 5,200 rpm. Torque exceeded 450 lb-ft from 4,300 rpm through 6,500 rpm.

Nitrous Installation and Testing

The ZEX Perimeter Plate was installed on the Speedmaster Funnel Web intake, requiring longer carb studs to accommodate the plate between the carburetor and manifold. The system was jetted for a 200-hp shot and the bottle heated to 92 degrees to achieve optimal flow pressure at 900 psi. High-flow nitrous and fuel solenoids - rated to support up to 300 hp - fed the system.

Ignition timing was retarded eight degrees in anticipation of the additional 200 hp.

Results: 563 HP to 775 HP

With the ZEX Perimeter Plate active, peak output climbed to 775 hp and 727 lb-ft of torque - exceeding the kit's 200-hp advertised rating on this carbureted stroker. The dyno graph shows a characteristic nitrous torque spike followed by a sustained power increase through the remainder of the pull.

Since nitrous power output is governed by bottle pressure and jet orifice size, the horsepower gains remain consistent across the rpm range. Activating a 200-hp shot below 5,252 rpm produces substantially more torque than horsepower - a factor that demands careful consideration of engagement rpm to protect drivetrain components not designed for the instantaneous torque load.

Key Takeaways

The ZEX Perimeter Plate's 12-point injection design delivered measurable results: even distribution, effective charge cooling, and power gains that exceeded the advertised rating. Paired with the Speedmaster Parker Funnel Web intake on this 363 Dart SHP stroker, the system demonstrated that proper nitrous plate design translates directly to dyno results. The system supports up to 300 additional horsepower with appropriate jetting.