Nitrous System Upgrade - Testing Day

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

John Nelson Dec 7, 2006 0 Comment(s)

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