The Combination
Before a part was ordered, we needed to find ourselves a car worthy of being sauced up. Our chosen lamb was the '89 Mustang GT belonging to Chris Winter of Crazy Horse Racing, who would also perform the install. If the car looks familiar, it should, as Winter was a participant in our naturally aspirated shootout (August '08 issue). The Fox-body features a stock-block 5.0L that has been punched out to 306 ci. The poked small-block Ford showcases a Comp solid-roller cam featuring 0.660 lift on both the intake and exhaust, as well as a set of World Products Windsor Sr. iron heads, an Edelbrock Victor intake, and a worked-over 750-cfm Holley carburetor. A full-on MSD ignition lights things off; fuel is supplied via an electric fuel pump and accompanying regulator; and the potent small-block is backed by a C-4 automatic trans, a 3,800-stall converter, and an 8.8-inch rear stocked with 4.56 gears. With a 13:1 compression ratio, the engine combination is not only out of the realm of running on straight pump gas, but it's also more suitable for the race track than for the street. Nevertheless, while we would have to change a few things to allow the car to run on the sauce, for all intents and purposes, this Pony was perfect for a shot of laughing gas via the Zex kit.
A Saucy Situation
What makes the Zex Perimeter Plate kit so different from the others on the market? It all revolves around the plate itself, which not only looks neat, but also showcases a different way of getting the nitrous and fuel into the engine.
With the carb out of the way,...
With the carb out of the way, we installed the bottom gasket, followed by the plate and the top gasket. The plate is clearly marked which side faces up. We also installed the plate with the fuel inlet forward and the nitrous inlet aft.
We sourced a wide-open throttle...
We sourced a wide-open throttle switch bracket from a local speed shop since the one that came with the kit didn't work with the car's carburetor linkage. Once we installed the switch to the bracket, we mounted the bracket to the passenger side of the carb body and checked for switch activation with the throttle wide open.
The plate Zex developed for its carbureted nitrous system is a perimeter plate that injects the nitrous and fuel in a 360-degree ring instead of using spray bar(s). "This is the only plate that Zex makes," says the company's Matt Patrick. "When we developed it four years ago, we wanted to do something different than the rest of our competitors. The plate has no spray bars. Instead, the nitrous and fuel is sprayed around the perimeter of the plate. This helps to improve the distribution of the nitrous as the 360-degree ring allows it to be sprayed evenly to each cylinder. A spray bar-type plate only aims at the runners, which can lead to certain cylinders getting more nitrous, and others less."
In addition, the manner and angle in which the nitrous is sprayed also helps it to act as a carburetor spacer. "The inverted cone-shape in which the nitrous is sprayed creates a low-pressure area between the bottom of the carburetor and the area, right before the air, fuel, and nitrous make their way into the intake manifold runners," Patrick says. "This low-pressure area allows the engine to pull in more air effectively. We've seen the plate alone boost power numbers by up to 30 hp."
We planned on mounting the...
We planned on mounting the bottle in the rear hatch area, which meant we'd have to drill holes in the floor. We didn't want to have to lower the gas tank to drill the holes, so we fabricated a couple of bracket mounts from steel lying in the Crazy Horse Racing shop. Once the modifications were made to the bottle brackets, they were measured and welded to the floor of the Mustang.
We switched out the worked-over...
We switched out the worked-over 750-cfm carb for a true 750 Holley replacement because the original carb was loading up the engine at idle. We installed the new carb and supplied studs and snugged it in place. In reality, we probably could've gotten away with a 650-cfm four-barrel, but the 750 worked nonetheless.
Once the carb was in place,...
Once the carb was in place, we mounted the fuel solenoid to the forward stud on the passenger side. After that, we mounted the nitrous solenoid on the driver-side rear stud.
The other interesting feature when it comes to the plate is Zex's trademarked Cryo-Sync technology. "We designed the plate not only to inject the nitrous in a different manner, but also, using our Cryo-Sync technology, to be a heat sink as well," Patrick says. "The super-chilled nitrous cools down the plate, as well as the carburetor and the intake manifold, leading to a denser intake charge and more power."
With Zex investing so much time and ingenuity into the carbureted system, we were curious if there was a similar setup for fuel-injected engines. "Currently, we don't have anything similar to this [carb] system for fuel injected applications," Patrick says. "To develop a system like this for the fuel-injected crowd that would utilize this sort of setup would mean catering to a small and select group of enthusiasts. If the need arises, then we'll look into it."
So how does this system stack up against a similarly constructed fuel-injected kit? "Both the carb systems and the fuel-injected systems do the same thing but operate on different principals," Patrick says. "Thus, the tune-up for each application is different."
After the solenoids were on,...
After the solenoids were on, we wrapped Teflon tape around the feed-line threads, and installed the lines to the solenoids. Be careful to not overtape the line, as you don't want small pieces of the tape to make their way into the solenoids.
We then hooked up the fuel...
We then hooked up the fuel lines to the carburetor.
To supply the fuel solenoid...
To supply the fuel solenoid with fuel, we had to tap into the main feed line. We did this by installing the Y-style fuel-distribution block, running one line to the regulator that feeds the carburetor, and the other line to the regulator that feeds the nitrous system. After fabricating the necessary braided fuel lines, we were good to go.
With the bottle secure in...
With the bottle secure in the rear hatch area, we hooked the nitrous feed line to the opening and ran the feed line through the car and into the engine compartment. The line ran inside, underneath the carpet along the driver side and exited through a hole in the firewall, where it was promptly attached to the nitrous solenoid.