ZEX Nitrous Perimeter Plate Makes Squeeze a Cinch

There’s many urban legends and old wive’s tales about nitrous out there keeping good, hardworking horsepower junkies from enjoying a little bit of added oomph. Using the super-simple ZEX Perimeter Plate kit, we’re going to walk you through how easy it is to install the nitrous on your carbureted muscle car in a manner of a couple of hours and help put to rest some of those myths and horror stories that have been spread throughout the years.

Nitrous does not need to be a scary enterprise. In fact, it's rather easy, especially with ZEX's Perimeter Plate Kit (PT# 82040) seen above.

Just The Facts, Ma’am

Most people unfamiliar with nitrous tend to believe that nitrous oxide is explosive. No, nitrous itself is not flammable. Nitrous, when introduced into an engine, allows the engine to burn more fuel per power cycle by condensing the ambient air, resulting in a form of supercharging, but in a liquid form instead of mechanical, like a roots-type supercharger or turbo system.

Most of the nitrous explosions we see are usually due to tuning the system for power gains well beyond the engine’s capabilities. Sometimes an improperly tuned system can result in fuel and nitrous being present in the intake manifold before the ignition is turned on. With the intake valve open, the starting ignition spark can cause an explosion in the intake manifold. Boom! The classic nitrous backfire.

Thankfully, today’s nitrous systems are very advanced and have many years of technology behind them, making them very user-friendly, and one of the safest and easiest ways to get major gains in horsepower and torque at the flip of a switch.

Making Easy Easier

For those running a single Holley or Edelbrock square-flange carburetor, the ZEX Perimeter Nitrous plate is incredibly easy to install, innovative and surprisingly affordable. Plus, there are no spray bars that might interfere with airflow into the motor or create turbulence.

We talked to ZEX’s Matt Patrick, who explained, “the Perimeter Plate allows an equal distribution of fuel and nitrous into the intake without any disruption of airflow into the intake,  allowing the intake to do what it was designed to do, without any disturbances from the introduction of the nitrous being injected.”

The ZEX plate has a 12-holes all placed in a 360-degree radius that give equal distribution of fuel and nitrous into the engine with an added benefit of immediate intake charge cooling, essentially serving as an intercooler for the engine when the nitrous is in use. Patrick continued, “The perimeter plate injects the nitrous so evenly that it has a greater cooling effect on the entire intake charge, and that in testing its not uncommon going from a spray bar system to the Perimeter Plate to automatically pick up a tenth or more with the same HP jetting.”

Best of all, the ZEX Perimeter Plate Kit (PT# 82040) is adjustable from 100-to-300 horsepower.

Look closely. See that rim of frost around the inside edge of perimeter plate? That's evidence of nitrous' cooling capabilities, which helps to compress the air in the combustion chamber making for a stronger charge.

Getting Started

Our guinea pig for our nitrous conversion is this stout street-prepped low-12 second ’69 Nova. Running a over-bored mouse motor 383, a TH350 and a 12-bolt posi, we couldn’t have asked for a better car to plumb up some extra horsepower. First, disconnect the negative battery terminal, remove the air cleaner and carburetor. This may require disconnecting your throttle linkage, vacuum lines, and hardware.

The secret to ZEX's perimeter plate is the series of 12 injection points where nitrous and fuel is evenly distributed through the intake charge, making for a balanced, efficient boost of performance.

Next, install the new longer carburetor studs with new gaskets and set the perimeter plate on the intake manifold, using a couple of carburetor nuts to secure the plate so you can mount the fuel and nitrous solenoids. This way, you can make any clearance adjustments before bolting the carburetor down for good.

Solenoids in Seconds

The fuel solenoid should be mounted up front and the nitrous in the rear. Once you have the solenoids mounted to the plate and checked for clearance of the fuel bowls and any linkage interference, you can bolt the carburetor on for good.

With your carburetor back on top of the intake manifold and linkage attached, mount the bottle in the trunk of the car; its the easiest and least conspicuous area to place it. If you have a trunk-mounted battery, mount the bottle on the opposite side to even weight distribution and be sure not to drill into (or through) the fuel tank when drilling the holes for the nitrous bottle mounts.

Next, decide if you are going to mount the nitrous line inside or under the car. If your running the line underneath, you’ll have to make sure the line is securely fastened to the frame rails and free from moving suspension components, such as the driveshaft or the heat of the exhaust. Use plenty of line clamps to secure the nitrous feed line and run it up so it ends behind the engine with enough slack to attach it to the nitrous solenoid.

Installing the ZEX Perimeter Plate is exceptionally easy. Simply disconnect your throttle linkage, unbolt your carburetor, install the longer carburetor bolts, slide in the ZEX plate between a pair of gaskets and reinstall your carburetor. The rest of the plumbing and wiring is equally as to-the-point.

If you decide you want the line inside the car, you will probably have to remove the rear seat and at least one door sill plate to feed the line to the front of the car where it will be safe from being snagged or stepped on beneath the carpet. When drilling through the firewall, always use a grommet where it passes through the firewall. Once the bottle and line are installed, you can connect the line to the nitrous solenoid.

The ZEX Perimeter Plate comes with both a fuel and nitrous solenoid, which ought to be installed at opposing ends of the carburetor. These will be wired and plumbed individually.

No Need to Call a Plumber

For the fuel side of the system, you will need to either tee off the fuel line or use one of the ports on your fuel regulator (that is, if you have one on the car), either way, it should be good for up to the 150hp setting.

Mount the fuel line away from any exhaust manifolds and install a good filter before the solenoid as well. It is a very good idea to have a separate fuel supply for the nitrous system if you plan on using the system past the 150hp settings. Also keep in mind its a very smart idea not to exceed the 150hp jetting without having forged pistons, especially with today’s fuels.

Also, a bit of good insurance is to install a Hobb switch on the fuel side. It will shut down the nitrous system in the event your fuel pressure drops below a preset pressure (usually 4.5 psi), preventing severe engine damage. We strongly recommend it.

You can now install the master arming switch inside the car. Run the power on a 15 amp circuit and then run the power lead through the firewall to the carburetor where you will connect it to the power leads to both solenoids.

Installing the micro switch to the side of the carburetor and adjusting it properly will program the system to activate when the throttle is fully depressed, providing your right foot complete control of the system delivery.

Next, attach the micro switch to the side of the carburetor and adjust it so that it is activated only when the throttle is fully depressed, that way you have some control over the system in case of severe wheel spin or if you just want to use the system for short bursts of power, instead of “all or nothing.” We find it helps when launching the car so that once you feel it hook, you can go “full throttle and bottle” just by pressing the gas pedal all the way.

When completely installed, your muscle car's engine compartment should look nearly unchanged, save for the short height increase of your carburetor and air cleaner and some wiring. We wouldn't really call this stealth, but it is clean.

One side of the micro switch should go to engine ground and the other two leads of both solenoids will go to the other terminal of the micro switch so that when the pedal is floored, it completes the circuit to the solenoids by creating a ground to open both the fuel and nitrous solenoids. Do not put power through the micro switch, as its not rated for that much voltage, use it for the ground only.

Shaking Out The Gremlins

Now it’s time for testing. Reconnect the negative battery terminal, but do not open the bottle, we will test for fuel first. Start the engine and make sure there are no leaks. You can now arm the system with the switch in the “On” position with the engine idling. Quickly touch the micro switch for just a second, you should hear the engine start to stumble due to the extra fuel that the solenoid just injected, that tells us the fuel side is working. You can shut the engine off.

Next, its very important that you disconnect the coil wire (or if you have an MSD box, remove the power lead) and make sure you have no spark when you crank the engine. If you have no spark, proceed by opening up the bottle, arm the system with the switch and check for any leaks.

The Nova we installed this ZEX Perimeter Plate Kit on already had a fuel cell in the trunk along with a battery on the other side, so we mounted the nitrous bottle behind the driver's side rear wheelwell.

If there are no leaks, then you can now test the nitrous side of the system by touching the micro switch for a second; you should here a loud click and a burst of pressure which is the quick release of nitrous into the intake.

Close the bottle, shut off the switch, and now crank the engine over without the coil wire attached for at least 30 seconds to rid the engine of any extra nitrous and fuel. You can now reconnect the coil wire and restart the engine.

You will need to reset the ignition timing for nitrous use; as a rule of thumb, retard the timing 4-to-6 degrees for every 100hp of nitrous. So, if you normally run 36-degrees of total timing and you’re looking to run a 100hp shot, you should back off the timing to about 30-degrees total.

This can be done also by installing a timing retard switch to your MSD ignition which can be controlled by a dial on the dash, or quite simply, you could mark the distributor with a line that you determine when you set it at 30 total, but that requires opening the hood to move the distributor every time you want to use your nitrous, and that’s no fun. There are also nitrous timing computers that you can add to control what rpm you want to activate the nitrous at and how much timing to to take out, if you want to go high tech.

You are now all set to try the system on the road. Open the bottle and run the car up through the gears and it will feel like you just swapped out your old powerplant with another engine when you floor the pedal. Have fun and try to avoid activating the nitrous under 2500rpms as it puts unwanted loads on the driveline and can cause detonation.

All in all, the ZEX Perimeter Plate System is a very good way to make safe usable power in a few hours in your own garage.

In the space of a couple hours, we were able to install, plumb and wire our new ZEX Perimeter Plate Kit on this '70 Nova. With just a couple minutes of double-checking, we had our freshly squeezed small block cranking out an extra 100-horsepower. Not too bad for a Saturday morning project, huh?

About the author

Scott Barlick

Opened my first speed shop in the mid 80s eventually starting up my auto machine shop business (Flo-Tech Racing & Machine) in 93 building engines ,specializing in porting and flow testing cylinder heads, along with many restorations and hot rod builds under my belt. Always having a passion for car stories I'm finally getting my feet wet with the online news contribution sector of the hobby.
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