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Nitrous System Upgrade - Testing Day

An Old Nitrous System Gets a Makeover, and it Pays Off at the Strip

John Nelson Dec 7, 2006

There's always room for improvement, the saying goes, and who are we to argue? On the other hand, our pal Dave Stoker was generally happy with the performance of his '67 Nova SS. Stoker has owned and raced his Deuce for eight years, and for six of those, many of his runs have been made on the squeeze. The car is a solid mid-11-second performer; last time out, in fact, Stoker ripped off a 7.19 eighth-mile, which ended his racing night, since the '67 has no 'cage. Stoker was running a bare-bones, old-school NOS Cheater system bought years ago. Would an injection of upgrades from the NOS catalog yield even better performance? We decided to find out.

The proof is in the numbers, so we'll only briefly explain what we did before moving on to the results. In general, NOS' extremely popular Cheater nitrous system hasn't changed in the years it has been on the market. Accordingly, our upgrades here mirrored the upgrades NOS has made. We replaced Stoker's old-style 10-pound bottle and high-flow valve with a new blue bottle and high-flow valve. More importantly, as you'll see, we also ordered two sets of NOS' Precision SS stainless steel jets to replace the motley assortment of old brass jets Stoker was running.

We also added some features that we consider nitrous necessities, even though they don't come in the basic kit. Chief among these is the blow-down tube, a safety measure you should have--and one tech inspectors will demand. Installing a purge kit was a bit of a challenge, but install it we did, since making sure the system is free of trapped air helps ensure consistent performance. Finally, we decided to try out the latest and greatest from NOS, the recently introduced P.O.D. system. According to NOS, the P.O.D. (Pressure on Demand) system seeks to take the guesswork out of maintaining correct bottle pressure. Long story short, the P.O.D. setup monitors bottle temperature and pressure through a transducer, and controls a bottle heater to automatically maintain a specified pressure. This is the most important of the system's many functions, since consistent bottle pressure is crucial to extracting maximum performance from a nitrous system.

In our case, however, the biggest key to max performance turned out to be a simple set of jets. Unlike the worn brass jets he'd been using, the new Precision SS jets came in precisely matched sets. Using the Cheater system jet chart, Stoker was able to dial in his nitrous shot with a much greater degree of accuracy. After a day at the track, running the various combos, Stoker was rewarded with a new fast e.t. And isn't that what it's all about when you're hittin' the juice? Read on to see the results of this nitrous re-do.


The primary duty of NOS' P.O.D. (Pressure on Demand) system is to maintain constant bottle pressure. It comes with this palm-sized controller, which allows the user to set the target pressure and temperature, check the actual figures, and work the remote bottle opener.

Dave Stoker likes to keep his Cheater system hidden, so adding a purge valve required some creative thinking. Luckily, the purge solenoid fit within the air-cleaner housing with the rest of the works. With just a bit of bending, the purge tube was routed through the passenger-side windshield washer.

Precision SS jets are made from stainless steel rather than brass. According to NOS, the tolerances are much more precise and won't change with wear and usage. Each and every jet is flow-tested before it leaves the factory.

0702ch_04_z Nitrous_testing 6/11

1. P.O.D. hookup is simple, requiring only a constant power source and a switched source.

2. The main controller box is mounted near the nitrous bottle; the black cable connects the controller to the controller/programmer unit.

3. By the time this story hits the stands, you'll be able to connect a progressive nitrous controller into the P.O.D. system, and even control it with the same keypad.

4. The nitrous pressure transducer allows the P.O.D. to monitor the actual bottle pressure.

5. A traditional pressure gauge provides a second way to check bottle pressure. 6. The P.O.D. also controls a remote bottle opener.

7. Bottle temperature is monitored via a temperature probe, placed under the heater straps.

8. The bottle heater is automatically cycled on or off as needed to maintain constant bottle pressure.

9. A blow-down tube provides an added measure of safety.

On the Motor
Timing: 40 degrees
1/4-mile: 13.31 at 102.85 mph
Notes: According to our subject '67 Nova's owner, Dave Stoker, the only change made on this run was to bump the timing from 36 degrees, where it was set for the car's last dragstrip outing, to 40 degrees. "That's where the motor likes to be," he told us, "and where it normally runs at."

Nitrous Run 1
Jets: 102 nitrous, 110 fuel
Shot: 325 hp
Timing: 36 degrees
1/4-mile: 11.56 at 116. 46 mph
Notes: For our first nitrous test, Stoker replaced the 73/82 brass jet combo, which the car ran during its recent 7.19-second eighth-mile, with the biggest set he had. According to Dave's dad, Terry, their goal was to set the system up for a great big shot while ensuring a safety margin by jetting it on the rich side. "We kicked the timing back down because of ignition issues last time out, but we still had misfiring issues. The car also felt very loose, spinning the tires from 60 feet out and on," Stoker reported. We think it's fair to say that the GM HEI ignition system was overwhelmed. Too much nitrous can actually blow out a weak spark.

Nitrous Run 2
Jets: 47 nitrous, 53 fuel
Shot: 100 hp
Timing: 40 degrees
1/4-mile: 12.18 at 113.11 mph
Notes: This was our first run with the new jets. We started out with a small shot, using a 47/53 jet combo from an NOS Super Powershot kit (Cheater kits start with a 150 shot). It wasn't the fastest run we recorded, but Stoker seemed to dig it. "We kicked the timing back up to 40 degrees timing, since this is where the engine runs best," he told us. "It spun the tires a little, but the car ran great. The engine would probably live forever at this level."

Nitrous Run 3
Jets: 63 nitrous, 71 fuel
Shot: 150 hp
Timing: 36 degrees
1/4-mile: 11.87 at 117.29 mph
Notes: Getting a bit more serious, Stoker moved the timing back because of bigger NOS jets, and his Nova responded. "It was a nice pass," he observed. "It spun a little more around the 1-2 shift."

Nitrous Run 4
Jets: 82 nitrous, 91 fuel
Shot: 210 hp
Timing: 36 degrees
1/4-mile: 11.13 at 119.31 mph
Notes: Stoker elected to skip the 180-horse shot listed in the Cheater jet chart and make a bigger change--and it turned out to be a good change. "This seems to be what the car likes," Stoker reported. And although he also mentioned that "It spun quite a bit in the middle of the track," this was out best test of the day, and a new fast e.t. for this car. The run also began to reveal the limitations of a factory HEI ignition system. "It had just a hint of misfire, like with the 250 shot," Stoker continued. "But it was very faint, and only during the last couple hundred feet of track.

Nitrous Run 5
Jets: 93 nitrous, 102 fuel
Shot: 250 hp
Timing: 36 degrees1/4-mile: 11.77 at 109.51 mph
Notes: At this point, the law of diminishing returns started to come into play. "It spun pretty hard for first the half of the track," Stoker told us. "And the ignition was misfiring from half track on." All in all, this combo was something of a step back.

Nitrous Run 6
Jets: 93 nitrous, 102 fuel
Shot: 250 hp
Timing: 34 degrees
1/4-mile: 11.22 at 120.89 mph
Notes: Not willing to give up on the 250 shot, the Stokers took another 2 degrees of timing out, but the results were a trade-off. We recorded our second fastest e.t. and our best trap speed, but with difficulty. "It still spun pretty hard," Stoker reported, "Though short-shifting it kept the ignition from misfiring until the end of track. It seems like the ignition is OK at lower rpm."

14745NOS--10-pound blue bottle, new style
16160NOS--Blow-down tube
13726NOS--Cheater jet kit
14182NOS--Nitrous P.O.D. system
15910NOS--Pressure gauge
16030NOS--Purge valve kit for AN-4 line
14156NOS--Stainless steel bottle brackets
13721NOS--Super Power Shot jet kit

* 400 small-block bored 0.030 over to 406ci
* Stock cast crank and rods, balanced
* Speed-Pro forged pistons, 9.7:1 compression
* Melling RV cam, stock rockers
* World Products Sportsman II heads with 64cc chambers
* Edelbrock Performer intake
* Stock Quadrajet carb
* GM HEI ignition
* 21/2-inch Corvette exhaust manifolds
* Edelbrock mechanical fuel pump
* Rebuilt TH350 with stock converter
* NOS Cheater nitrous system
* Stock springs front and back
* Lakewood 90/10 shocks
* Homemade traction bars
* Car weighs 3050 without driver
* All tests run with 11.5-psi tire pressure
* All times corrected



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