Zex Perimeter Plate Nitrous Kit Mustang Install and Test - Dinner Is Served

Speaking of the tune-up, Patrick offers some pearls of wisdom when it comes to setting up the car for the hit of the sauce. "Most of the time, a change in the jets of the carb isn't needed, as the wet kit will feed the extra fuel into the engine via the plate," he says. "For starters, you should go with a spark plug that is two heat ranges colder than stock. Most of the plug gaps we see are between 0.040 and 0.045 inch, so make sure the gap is closed up to between 0.032 and 0.034 inch. Tightening up the gap allows the spark to jump the gap. Nearly 9 out of 10 times, the gap is too wide, and the spark gets blown out under the increased cylinder pressure.

"A good rule of thumb is that when you're using a 150hp shot, only a spark-plug upgrade is required. When you go with a bigger shot, something like 300 hp and up, an aftermarket ignition system is highly recommended. When it comes to ignition timing, a good thing to remember is that for every 50 hp of nitrous, retard the timing 2 degrees. I recommend this for anyone using a nitrous setting of more than 50-75 hp."

One thing Patrick was adamant about was setting the fuel pressure for the carbureted system. "To properly set the fuel pressure with any carb kit, you need to have the fuel source for the plate in a flowing condition. This means that if you have an electric fuel pump, turn the key on and get the fuel pump to flow fuel. Without flow, you can't properly and accurately set the fuel pressure, as you can be off between 3 and 4 psi. We like to see 6 psi of flowing fuel pressure for the inlet side of the nitrous kit, and highly recommend our fuel flow check tool to properly set and monitor the fuel pressure."

Doing The Deed
With all of our questions answered, it came time to do the deed. We cruised to Crazy Horse Racing in South Amboy, New Jersey, where Winter and his Mustang waited patiently for us to arrive with the kit and our camera. Before we even popped the Mustang's bonnet, we put the Fox-body on a lift and yanked the 4.56 gears out of the 8.8-inch rearend. We replaced them with a set of Ford Racing Performance Parts 4.10s that we sourced from Down's Ford in Toms River, New Jersey. The 4.56 gear ratio was perfect for allowing the 306ci engine to scream through the lights naturally aspirated, but once the nitrous was activated, chances were good the car would run out of gear well before the finish line. The 4.10s would hurt the Stang a bit when running sans sauce, but would help it use all of its available power range when the laughing gas was activated.

We also switched the worked-over 750-cfm Holley carburetor for a plain 750-cfm Holley four-barrel. With the work that was performed on the first 750 carb, it was flowing in the neighborhood of 950 cfm, which was way more than what this little 306 needed. Even the straight-up 750 carb we replaced it with was probably too big, as we had to lean the jets out a few sizes to get the air/fuel ratio in the 12:1 range. If we could have slapped a 650-cfm carb on this puppy, the Mustang might've been a bit happier, but in the end, things worked out just fine.

Compared to an EFI kit, the Zex carb kit is fairly straightforward and easy to install. The kit comes without the bells and whistles such as a purge kit and a bottle heater, so the only wiring that needed to be done was the wiring of the solenoids to a power source, the crimping of the wires to the wide-open switch, and a button to arm and activate the system. As for plumbing, Zex supplied more than enough braided line to run from the bottle's mounting position in the rear hatch area of the Mustang up to the nitrous solenoid. We had to order a few other fuel-system pieces (second regulator, Y distribution block, and braided line) to siphon off fuel from the main fuel line to the fuel side of the system, but for all intents and purposes, the kit can be installed in a day.