Nitrous Install - Cheap Street Chevelle

The response to Car Craft's project Cheap Street Chevelle has been amazing. Readers have been sending in loads of mail offering advice on what mods should be done to Cheap Street to make it even better and faster. And that's the goal of this project--to use the car as a test mule for upgrades that readers want to see.

Most of the letters we get focus on making the Chevelle quicker in the quarter-mile. Of the "horsepower hungry" letters, many want to know how effective nitrous oxide really is. Does nitrous really deliver the power that it claims?

01. When you order an NOS... 

   

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01. When you order an NOS Super Power Shot nitrous kit (PN 5401 for Holley carbs, PN 5104 for Q-Jet carbs), it comes complete with a full 10-pound-capacity nitrous bottle, an injector plate, nitrous and fuel solenoids, filters, fittings, three stages of nitrous/fuel jets (for 100, 125 and 150 horsepower), switches, aircraft-quality stainless-steel braided hose, assorted mounting hardware and installation instructions. If you desire other items, such as additional horsepower range jets or a throttle-activated on/off switch, these items are available through NOS for an additional charge.

Car Craft reader Greg McGee wrote:

I've got a '67 Mustang with a 10:1 small-block V8 engine, a Holley 650-cfm carb and a street/strip cam. The car has a C4 automatic transmission, 2500-stall converter and 3.70:1 rear gears. So far my Mustang has run a best e.t. of 13.46 at 101 mph. How effective will a basic nitrous kit (not a big, full-race nitrous setup) be for my Mustang? Since your project Cheap Street Chevelle has similar parts to my car, maybe you can install nitrous on your car to see how much quicker it goes and how reliable it really is.

Well Greg, ask and you shall receive. This month we're installing a basic nitrous-oxide setup on our Chevelle to see if we can knock some notable time off of our e.t.'s--not just a tenth or two. We contacted the folks at Nitrous Oxide Systems (NOS) in Cypress, California, to help us choose a basic system. By basic we mean an adjustable kit that offers a power increase up to about 150 horsepower. Although NOS has dozens of nitrous kits available (including its extremely popular 250hp Cheater kits), the technicians recommended a more tame Super Power Shot series kit (PN 5104). The kit comes with everything needed to install the system and is fully adjustable between 50 and 175 horsepower, making it perfect for our daily driver Chevelle. In addition, the Super Power Shot is affordably priced at about $350, making it perfect for a street machiner on a limited budget.

If you've been keeping up on project Cheap Street Chevelle, you know that it recently got a new low-buck engine (which produced 355.6 horsepower). The engine was strong enough to power the car to consistent 13.5-second e.t.'s. Since then, we've rebuilt the stock TH350 transmission, installed a new Carter mechanical fuel pump (the stock fuel pump was starving the engine at high rpm) and bolted on a set of sticky Mickey Thompson 26x8.5-inch E.T. Drag slicks for track testing. Before installing the nitrous system, we retested the car with the new tranny, fuel pump and slicks in place. We're happy to report that our rig ran a 13.18 at 100.33 mph, which was immediately backed up with a 13.19 at 100.03 mph through the mufflers!

02. Begin the nitrous install...        read full caption 02. Begin the nitrous install by disconnecting the battery cables to avoid any sparking mishaps. Then disconnect the carburetor fuel lines, throttle linkage, return springs and transmission kick-down cable(s). Then carefully remove the carburetor, making sure not to drop any bolts, washers and/or gunk inside of the intake manifold.	03. Being that our Chevelle...        read full caption 03. Being that our Chevelle runs a 750-cfm Q-Jet carburetor atop an Edelbrock Performer intake manifold, it uses two studs in the rear and two long bolts in the front to hold the carb in place. Because the NOS nitrous injector plate goes between the carb and the manifold, longer studs and bolts are required to provide the additional mounting threads to make up for the added thickness of the nitrous plate. Simply unthread the original carb mounting studs/bolts and thread in the new studs supplied in the NOS Super Power Shot nitrous kit.	04. Install the new intake-manifold...        read full caption 04. Install the new intake-manifold base gasket (included in the kit) and carefully set the nitrous injector plate in position--the fuel port faces forward and the N2O port faces toward the rear (it is marked on the plate). Because our NOS kit is for a Q-Jet carb, the nitrous plate has special kick-outs to clear the carb's large secondary throttle blades.
05. One of the biggest mistakes...        read full caption 05. One of the biggest mistakes rookie nitrous installers make is using Teflon(R) tape to seal the pipe threads on the various nitrous fittings. The tape is often applied improperly and either comes unraveled from the threads or gets sucked into the nitrous and/or fuel line and clogs the jets. This leads to rich/lean conditions and big problems. NOS recommends using a dab of liquid Teflon(R) thread sealant. Don't smother the threads with the sealant, just add a dab. As you tighten the fitting in, the sealant will work its way into the threads and form a tight seal.	06. After adding a dab of...        read full caption 06. After adding a dab of Teflon(R) thread sealant, carefully install the special fuel filter that bolts directly to the NOS fuel solenoid. Be sure to snug up the filter with a wrench, but don't overtighten the unit, or the tiny threads will probably strip. The extra fuel filter keeps the fuel portion of the nitrous system from getting clogged, which would cause a lean condition that can destroy an engine.	07. Installing the nitrous...        read full caption 07. Installing the nitrous and fuel jets into the injector plate is easy. Simply insert the jet (with its tapered end facing outward) into the fitting opening until the jet fully seats. Then add the L-shaped tube (included in the nitrous kit) and carefully tighten the nut. Do not overtighten the nut, because it only takes a slight bit of pressure to properly seat/seal the jet. Once again, overtightening will likely strip the tiny threads.
08. After installing and tightening...        read full caption 08. After installing and tightening the L-shaped tubes (one leading to the fuel solenoid and one to the nitrous solenoid) to the injector plate, carefully thread on and tighten the tube to the fuel and nitrous solenoids. Notice the auxiliary fuel filter in the fuel solenoid.	09. Normally, the fuel line...        read full caption 09. Normally, the fuel line would come up from the fuel pump and feed directly into the side of the carburetor. However, for the Super Power Shot nitrous kit you must cut the fuel line and splice in a special T-style fitting (supplied). This fitting allows fuel to be delivered to both the carb and the fuel solenoid of the nitrous system. Try to keep all fuel lines as short as possible and away from hot engine components and rotating parts (such as the fan and pulleys).	10. Although not required,...        read full caption 10. Although not required, it's a good idea to change the fuel filter in the carburetor while the carb is off of the vehicle. With a new filter in the carb and an auxiliary filter for the nitrous system, the engine will only see clean fuel and will deliver peak performance.
11. Once the nitrous and fuel...        read full caption 11. Once the nitrous and fuel solenoids have been hooked up, add the new carb-to-nitrous plate gasket (included) and tighten the carb down with the new bolts. Earlier, the longer carb studs were added for the rear of the Q-Jet carb, but you'll also need to install the longer bolts (included) that tighten down the front of the carb. After the carb is tightened down, reinstall the fuel line and various vacuum lines (such as the one that goes to the distributor). Fully open and close the carb's throttle blades a few times to ensure that everything operates correctly and nothing binds.	12. Although the NOS Super...        read full caption 12. Although the NOS Super Power Shot nitrous kit comes with the hardware to mount the activation switches in the cockpit of the car, we chose to upgrade to a throttle-activated switch (PN 15640). This switch activates the nitrous system only when the carb is in the wide-open-throttle position. The switch is a great safety feature--if the throttle is backed off slightly, the nitrous system shuts off automatically. This thwarts backfires, lean conditions and so on. Plus, the switch increases dragstrip consistency because it activates at W.O.T. each time, not when the driver thinks the engine is at W.O.T. To install the switch, simply bolt it on the intake manifold in a position that allows the carb linkage to swing back and depress the switch at full throttle.	13. Whether you use a handheld...        read full caption 13. Whether you use a handheld or a throttle-linkage-activated nitrous switch, you'll need to mount the special relay in a clutter-free area away from hot engine parts. We fastened our relay on the firewall just rearward of the master cylinder. Hook up the various power, ground and solenoid activation wires to the relay as the instructions show. All wiring is straightforward and easy--no degree in electrical engineering is needed.
14. After mounting the relay...        read full caption 14. After mounting the relay switch, run the necessary wires through the firewall and into the cockpit. Mount the on/off switch(es) in a convenient location near the driver. Being that we're not smokers, we mounted our switches on the bottom of our ashtray. When the need for nitrous arrives, simply flip the switch and you're ready for action. The switch on the left is for our bottle heater (optional) and the other is our on/off switch.	15. Begin the bottle mounting...        read full caption 15. Begin the bottle mounting procedure by slipping the mounting brackets onto the nitrous bottle. Only snug the bolts finger-tight at this point. Install the taller bracket on the valve side of the bottle and the shorter bracket at the bottom of the bottle. If you reverse the brackets, the siphon tube inside the nitrous bottle won't properly pick up the nitrous oxide, and problems will result.	16. Pick a clutter-free, sturdy...        read full caption 16. Pick a clutter-free, sturdy area in the trunk to mount the nitrous bottle. We chose the passenger side of the trunk just rearward of the wheelwell as our location. Using a felt-tipped pen, mark around the base of the mounting brackets and the bracket bolt holes. Then remove the bottle and bracket assembly from the trunk. Use a handheld drill to drill out the necessary mounting holes for the brackets.
17. Once the necessary bolt...        read full caption 17. Once the necessary bolt holes have been drilled, install and tighten the bottle brackets to the trunk floorpan. Then re-install the nitrous bottle and tighten the straps in place. Notice the strap and wires wrapped around the nitrous bottle. This item is an optional NOS bottle heater (PN 14164) that heats the bottle to a specific temperature dictated by a small, built-in thermostat. The best (and most consistent) results from nitrous oxide occur when the nitrous delivery pressure is about 900 psi. As temperature drops, so does the nitrous pressure, and this affects dragstrip e.t.'s (due to rich or lean conditions from inconsistent pressure). The thermostat keeps the bottle temperature at about 80 degrees even if cool nighttime temperatures drop below 0 degrees! An in-car switch activates the heater.	18. Once the nitrous bottle...        read full caption 18. Once the nitrous bottle is securely mounted in position, determine the location where the braided line from the bottle valve will pass through the trunk floorboard. Carefully drill the necessary hole, making sure not to puncture anything that may be on the underside of the trunk. Afterward, deburr the hole and run the braided line up through the hole and onto the nitrous-bottle valve.	19. We opted to install a...        read full caption 19. We opted to install a nitrous pressure gauge (PN 15910) so we could monitor the nitrous-bottle pressure. Paired with a bottle heater, the nitrous system is much easier to tune and will be more consistent. Before each run, check the bottle pressure to ensure that it is about 900 psi. If not, simply flip on the bottle heater and you'll be ready for action.
20. Run the other end of the...        read full caption 20. Run the other end of the braided nitrous line up to the engine-compartment area and mount it to the nitrous solenoid. Rather than tie-wrapping it to the car frame and nearby hardware, we took a little extra time to snake the line through the framerails all the way up to the front of the car. Because our braided line is within the framerails, the chances of it being snagged or damaged by nearby moving parts are greatly reduced. Notice the tape over the end of the line. This prevented dirt and crud from getting inside the line while we routed it under our not-so-clean '70 Chevelle.	21. This is what our final...        read full caption 21. This is what our final trunk-mount nitrous-bottle setup looks like. It's securely fastened to the trunk floorboard, has a bottle heater (optional) with necessary wiring and remotes, is mounted at the correct angle and has an inline nitrous psi gauge. Simply open the main-bottle valve, arm the system by way of the in-cockpit switch and hold on. Note: Whenever you're done with or not using the nitrous system, always turn off the main-bottle valve. This prevents the high nitrous pressure from exerting unwanted force on the small seals in the nitrous solenoid, which can cause them to swell. In other words, don't leave the bottle turned on overnight.	22. We had awesome results...        read full caption 22. We had awesome results with the NOS Super Power Shot nitrous system. We tried different nitrous power levels to evaluate their effects on quarter-mile performance. However, we didn't go up to full power (largest jets) because we didn't want to overtax our mechanical fuel pump and hurt the engine. If we were to add an auxiliary electric fuel pump with a fuel-pressure regulator, we could use the full potential of the nitrous system. However, running the middle jet setting (125 horsepower), we reduced our e.t.'s from a 13.18 at 100.3 mph to 12.29 at 109.3 mph through the mufflers! That's a 0.9-second reduction in e.t. with a 9-mph increase in trap speed--not bad for a $350 NOS nitrous kit and a day's worth of install time. The best part is, with the Mickey Thompson slicks hooking and running nitrous off the line, our Chevelle would pull its left front tire off the ground about an inch. After the track tomfoolery, we drove the car home (more than 50 miles away) without a problem and later drove it to a cruise-in.