Don't tell me you haven't seen it. I know Corvette guys aren't supposed to like Mustangs, but if you're into car culture, you've definitely seen the part in Gone in 60 Seconds where Nicholas Cage flips the nitrous-arming switch on the '67 GT500 he's stealing, hits the little red button marked "go-baby-go," and loses the police helicopter that's closing in on him. Thanks in part to that scene, and the Fast and Furious franchise, nitrous oxide has steadily increased in popularity over the past several years.
Among the newer nitrous products is the adjustable Perimeter Plate system offered by Zex, which adds between 100 and 300 horsepower and is designed to overcome some of the weaknesses of traditional "plate"-style nitrous systems. Here, we'll look briefly at what nitrous is and does, and then take a more in-depth look at how to install the Zex kit on my red '72 small-block coupe, AKA "Scarlett."
Though still frequently considered a somewhat naughty addition to a car (note how many of the kits have "sneaky" or "cheater" in the name), using nitrous oxide to increase engine power is nothing new: As far back as World War II, the Nazi Luftwaffe used it to help airplane performance at high altitude. Not actually a fuel, nitrous oxide is composed of two parts nitrogen and one of oxygen; the latter element is released as the compound breaks down at high temperature. This aids the process of oxidizing fuel so that more can be burned, thus increasing the engine's power output.
The reason there's "no replacement for displacement" is that more room allows for more fuel to be burned. Nitrous essentially accomplishes the same thing in a smaller space, with little modification required to the engine. And unlike stroker kits, turbos, or superchargers, the extra power is only produced on demand, leaving fuel economy and general driveability unaffected.
Nitrous systems are generally divided into two types. In a "wet" system, the nitrous is mixed with additional fuel and sprayed into the intake tract. In a "dry" setup, the nitrous is sprayed by itself, and the fuel delivery system is calibrated or modified to deliver the additional fuel needed. One of the advantages of a wet system is that, since the fuel and nitrous are sprayed together, it's simpler than a dry system. This reduced complexity somewhat lessens the possibility that the nitrous will be sprayed in without the extra fuel.
Should the engine run lean (i.e., without sufficient fuel) while nitrous is being added, the result will be very high combustion temperatures, coupled with really good odds of engine damage. You've heard of melting pistons, and burning holes in them? Yep. That's why you'll need to be careful.
With a little caution, however, there's nothing to fear. Estimates vary, but assuming your engine is in good shape and unmodified, anything between 100 and 150 horsepower should be safe to add. Much over that, and you're going to need to beef some things up.
In this case, the engine we'll spray is a low-mileage ZZ2, a GM crate motor producing somewhere in the neighborhood of 345 hp and 400 lb-ft of torque. The kit Zex sent contained a Perimeter Plate for a standard Holley application (the company also has one that's Dominator compatible), fuel and nitrous solenoids, an assortment of jets, all the braided-steel line and electrical components required for installation, and a 10-pound nitrous bottle and mount. While mine came in Zex's trademark purple color, the kit is also available in a stealthy "Blackout" version. The bottle comes empty: Expect to pay around $4 per pound to fill it.
1 Put the mounts on the bottle...
1 Put the mounts on the bottle and place it where you want it to install it, being aware of any supports under the floor. Use masking tape under the mounts to mark the drill locations, since you'll have to remove the brackets to drill the holes. Drill from the top and use the included bolts and washers to mount the bracket. The carpet will tend to wrap around the drill bit, so you'll need to clean it every so often.
2 Route the braided line...
2 Route the braided line to the bottle by feeding it through the firewall, down behind the dash, and under the center console and e-brake housing. From there, you can either tuck it under the carpet and bring it over the top onto the back deck, or route it through a hole under the rear of the e-brake housing and up into the storage well that holds the jack.
3 Start the plate-mounting...
3 Start the plate-mounting process by removing the air cleaner and everything attached to the carb, beginning where the cable meets the linkage on the outside. Next, unhook the return spring and loosen the clamp that holds the throttle cable. Since the throttle-cable bracket is held in place by the nut holding the carb on its stud, it'll have to go, too. Also note the large stud sticking up out of the center of the carb--we'll deal with it later.
4 The throttle cable is off,...
4 The throttle cable is off, and released from the clamp. Now for the springs...
5 Next, loosen the nuts that...
5 Next, loosen the nuts that hold the carb down on its studs; there should be one at each corner of the carb, and one of them will likely be holding the throttle cable bracket.
6 Disconnect the fuel line....
6 Disconnect the fuel line. In our case, that simply required loosening the hose clamp that held the fuel line to the inline filter. Place a can under it to catch the fuel that’s about to pour out.
7 Disconnect the vacuum lines...
7 Disconnect the vacuum lines coming from the carb and lift if off. There should be one vacuum line at the front, and a larger one at the back, which was
8 Put a clean towel in the...
8 Put a clean towel in the intake to prevent anything from falling in. Replace the carb studs with the included longer ones, which are required to accommodate the added height of the nitrous plate. The old ones should simply unscrew; if they’re stuck, a pair of Vise-Grips should break them free.
9 Lay the plate in place,...
9 Lay the plate in place, with one of the two included gaskets under it. While Zex suggests assembling the hoses later, you may find it helpful to temporarily