Category: Automotive & Industrial

Installing nitrous the right way

Reading time:

When applied properly, nitrous oxide is the easiest, least-expensive way to make power, and it’s relatively easy to install. To show how easy it can be to add a couple hundred horses by bolting on a bottle, we installed a Nitrous Works adjustable plate system. The 75-225hp kit is one of The Nitrous Works’ most popular because of its ease of installation and adjustability.

If you get greedy for more power later, you can swap out a few components (solenoids and plate) to bring the system up to a 325hp maximum. That’s potentially doubling the power of a mild small-block with the hit of a button! Of course, at higher power levels the engine must be configured to take the added horsepower, and an excellent fuel and ignition system is required. While those upgrades aren’t difficult, they can be time consuming and add considerably to the cost of the nitrous installation.

A squeezed 450 horsepower small-block will still be far less expensive and infinitely more streetable than a non-nitrous’d 450hp version of the same displacement.

Remember that the keys to safely making power with nitrous are providing enough fuel and retarding the ignition sufficiently. But enough soapbox preaching; it’s time to get dirty and install that nitrous system.

  • 1 A complete plate system from The Nitrous Works (TNW) comes with a plate, two solenoids, 16 feet of -4 nitrous line, a nitrous bottle, a fuel filter, nitrous and fuel jets, electrical switches and connectors, and mounting hardware for the bottle.
  • 2 To mount the bottle, strap the brackets to it and set it in place. Mark where to drill the holes, but be sure there isn’t anything under the floor where you want to drill (the gas tank, for example). The valve on the bottle should face forward and up, and the front should be higher than the rear (one pair of brackets is taller) so that the pick-up tube inside the bottle is located where the nitrous will be under acceleration.
  • 3 The most convenient place to mount the -4 nitrous line is parallel to the stock fuel line. Always be careful that the braided line clears all moving parts, and isolate it in rubber mounts to avoid abrasion. Before making the connection to the nitrous solenoid, blow debris from the line by having someone open the valve on the bottle while you hold the line away from the car with a rag. Don’t hold the line with your bare hand or allow the nitrous to hit your skin; the nitrous is at sub-freezing temperatures when released, and frostbite can occur.
  • 4 A TNW product that we highly recommend is its safety system. The system consists of two Hobbs switches that monitor fuel pressure and oil pressure. When either switch senses low pressure, a safety solenoid opens, releasing the nitrous into the atmosphere rather than your engine, saving a potential disaster. The vent tube should be routed to exit in front of the windshield to alert you of a problem immediately. However, be sure it’s not pointed at the windshield because hot glass and freezing-cold nitrous don’t mix well.
  • 5 Fittings are provided with the safety system to “T” into the nitrous and fuel-solenoid lines, but you will need to purchase one for the oil line. We also added Earl’s -3 Speed-Flex stainless-steel-protected extruded Teflon hose to replace the TNW hard lines to plumb the solenoids and the plate. That allowed us to mount the solenoids to the valve cover bolts on brackets we fabricated for a relatively clean installation. Don’t forget to install the nitrous and fuel jets.


Inadequate fuel supply is the leading cause of nitrous-related problems. Nitrous simply adds more oxygen to the engine. To keep your air/fuel ratio correct, more fuel must also be added in a proportional amount. If you are using a system configured for less than 125 horsepower, you can get away with using stock fuel lines, but you should add a quality high-volume fuel pump. If you plan to exceed a 125hp increase, it is recommended that you run a dedicated fuel line (-6 is recommended up to 300hp and -8 after that) for the nitrous system. Use the stock fuel line to feed the carburetor or run an additional -6 line for it and a separate fuel pump and regulator. That can be expensive, but you won’t regret the investment in your fuel system.

Regardless of the power level, most street cars can use the additional fuel pressure a quality high-volume pump provides. Mallory has eight models of electric fuel pumps. Its Comp Pump Series 140 is an excellent choice because it is capable of being regulated to work on bone-stock engines or very-high-horsepower applications. It is also easy to install and operates very quietly. If you’re using rubber lines (which is okay in lower-hp applications), then Mallory sends the necessary fittings. We upgraded our system with Earl’s -8 Perform-O-Flex line, requiring two 45-degree fittings for the fuel filter as well as one straight fitting and one 90-degree fitting for the fuel pump.

Of course, it’s difficult to set your fuel pressure or be sure it is adequate as you run through the gears without a good fuel-pressure gauge. We chose an Auto Meter Pro Comp gauge (part No. 5413) with an isolator so the gauge could be safely mounted inside the car. You will also need a -4 line to connect the isolator to your fuel source. Auto Meter offers these in 3-, 4-, and 6-foot lengths. The Mallory Comp Pump 140 comes with a regulator that allows you to vary fuel pressure from 6 to 12 psi.