If I told you we recently bolted up a nitrous kit and gained nearly 200 rwhp and 300 lb-ft of torque, would you believe it? Would it grab your interest? If so, keep reading because we did in fact find sick power after installing Nitrous Pro Flow's Cheap Street nitrous kit on a typical 5-liter Mustang.
Long-time fans of MM&FF may remember the 317-inch small-block that B&B Performance Machine (Rahway, New Jersey) assembled a few years back. We covered the in-depth buildup and subsequent dyno test of the mill that pumped out 500 hp at the flywheel. The engine was stuffed in a hot little '86 GT--backed by a Nash five-speed--but never really got wrung out at the track.
In the past few months, the Nash gave way to an AOD, and the new owner, Dan Ryder of Danny's Pro Performance in Keyport, New Jersey, was found tuning the GT on his Dynojet chassis dyno. Ryder and I joked about throwing a shot of nitrous at it, and before you know it, I made a call to Nitrous Pro Flow and they shipped us a single-stage Cheap Street kit. The kit is easy to install and designed to add between 50-225 hp.
As I just mentioned, the engine is a strong one indeed. It's not too trick, but not a time bomb either. B&B used a Mexican 5.0 block and stuffed in a nitrited and stroked crank, Eagle rods, and Ross flat-top pistons. Dave Jack ported a set of Trick Flow Specialties heads, and the casts now flow close to 300 cfm. A Comp Cams solid roller was installed along with Comp Cams lifters and rockers, and the ignition is from MSD. VP C-12 race fuel is supplied by a BG 280 pump, and a pair of BG regulators keep the pressure at 7 1/2 psi. Exhaust flows through 1 3/4-inch headers and two-chamber Flowmasters with dumps.
After dialing in the jetting and the timing curve, the 317 made 400.1 hp at 7,000 rpm at the tires, and torque topped out at 346.9 at 5,400 rpm. We think those figures are pretty impressive considering the AOD, and we were expecting big things once the nitrous was installed.
The Cheap Street kit is impressive looking, and it includes a 10-pound bottle and brackets, line filter, main feed line, single-stage plate with burst panels and solenoids, jet kit, and an attached purge solenoid. Nitrous Pro Flow's kits are mainly for racing applications, and some of the little items must be supplied by the end user. These include an arming switch, activation switch, a 30-amp relay, and some of the wiring. Nevertheless, the kit does include one of the best instruction manuals we've seen, and the solenoids come partially wired with a weather-pack connector.
Included in the manual is a clear and concise wiring diagram. In addition, there are recommended settings for timing, fuel pressure, and type of fuel to use, along with nitrous and fuel jetting and the level of performance that should result.
Spray Time
As I stated before, this bad boy made exactly 400.1 hp in naturally aspirated trim, and we were anxious to see how much power it would make with our old friend Mr. Nitrous pumping through the engine.
Ryder and I wired and plumbed the nitrous kit, which took the better part of a day. We had some small clearance problems between the solenoid bracket and our oversized valve covers, but we solved the problem by installing a 1/2-inch Moroso spacer below the nitrous plate. And since Ryder plans to swap the AOD for a C4, we decided not to make a bracket for the activation switch (at this time). Instead, we connected a button and activated the juice from the cockpit.
For fuel, Nitrous Pro Flow suggests Union 76 Pro Stock 118, Torco 118 NOS, or VP C-16. All we had was VP C-12, so that's what we used. Nitrous Pro Flow also recommends spark plugs that are two heat ranges colder, and we didn't have those either. This didn't stop us; it just kept us from going all the way to the 225 shot.
Once the install was complete, we filled the bottle and heated it with a bottle warmer until it reached 1,000 psi. As per the instructions, we then retarded the timing by 5 degrees (from 34 to 29), and then it was time to go. Ryder nailed the gas, hit the juice, and the 317 went from a yell to a scream. It was noticeably louder than before, and redline came in an instant. We revved the little mill to 7,300 rpm before shutting it down, and the Dynojet quickly calculated the numbers and spit out the results. The screen showed 491.8 hp at 6,900 rpm and 472.5 lb-ft of torque at 4,300 rpm. A back-up run was made and the engine repeated with 490 hp and 469 lb-ft of torque, and we were very, very happy. The air/fuel meter on the Dynojet showed an average of 11.8:1, and the plugs looked perfect--despite not really being cold enough for nitrous use.
Rather than go up incrementally, we jumped right in and slipped the #73 jets in the fuel and nitrous lines. In lay terms, this was supposed to be the 175 shot. The timing was backed off another 4 degrees (25 degrees total), and we made a pull. When Ryder nailed the gas, the Mustang stood up and tried as hard as it could to take off. The rear wheels rolled at a rapid pace and grew as the rpm climbed. Once again, Ryder took the beast to 7,300 and clicked it off. The sound of horsepower filled the room, and the dyno recorded 585 hp at 6,600 rpm and a whopping 636.0 lb-ft of torque at 3,600 rpm!
We were shocked by the power gains and really wanted to go for the big 225 shot. But we didn't have colder plugs or the recommended race gas, so we remained content with the results and called it a day. In total, the 317 gained 185.4 hp at the wheels and 280 lb-ft at the wheels. That, my friends, equals about 222-flywheel hp and a gain of 347 lb-ft of torque at the flywheel. And if you can believe it, using 20 percent power loss through the AOD, the total flywheel power now equals 702 hp and 763 lb-ft of torque.
The Pro Flo kit comes with the solenoids already wired to one side of the weather-pack connector, but the owner must complete the wiring on the vehicle side. Fortunately, there are clear instructions and a wiring diagram to show you how it's done. | 
After wiring the vehicle side of the connector, Ryder slipped the two halves together. | 
It is necessary to install a 12-volt, 30-amp relay to power the solenoids (see wiring diagram). |
It all takes place at the Nitrous Pro Flow plate. The plate comes ready to go with the attached bracket and solenoids. It was necessary to make a line for the purge, which we did and routed to the cowl. | 
The plate comes equipped with six burst panels designed to blow out in the case of a backfire. It is much easier and cost effective to replace a burst panel or two, rather than an intake, carburetor, or worse. | 
Once the nitrous lines and wiring was completed, we reinstalled the carburetor. |
Ryder added a second BG fuel regulator to feed the fuel side of the nitrous system. Nitrous Pro Flow recommends setting fuel pressure to 7 1/2 pounds with race fuel and 8 1/2-9 pounds with pump gas. | 
Our small-block is now cocked and ready to rock. | 
Before hitting the juice, we made one last wiring check and looked for any fuel or nitrous leaks. |
Houston, we have purge. | 
Without the benefit of nitrous oxide, the 317 produced 400.1 hp at 7,000 rpm. | 
With Nitrous Pro Flow's Cheap Street kit setup with the #50 (100 hp) jets, the engine pumped out 491.8 hp--a gain of 91.7 ponies at the wheels. |
For our engine, Nitrous Pro Flow recommended changing to plugs that were two heat ranges colder and to a gasoline with higher octane. We didn't have either, so we limited the engine to the 175 shot. This is the result. Total gain is 185.4 hp and 289.1 lb-ft of torque and, best of all, the plugs and air/fuel still looked great. | 
Nitrous Pro Flow kits come with a nice instruction manual that includes this wiring schematic. There is a diagram for single stage (shown), one for two-stage, and plenty of tuning recommendations. | 
And then we backed the timing from 34 degrees total advance to 29 degrees BTDC. |
We started with the #50 jets in the nitrous and gas lines. Nitrous Pro Flow's literature stated that this should equate to 100 additional horsepower at the flywheel. | 
With the #50 jets in place, we tightened the lines and let it rip. The results were instant, as our 317 jumped from 400.1 hp at 7,000 rpm to 491 ponies at 6,900 rpm. Equally impressive was the torque, which climbed from 346.9 at 5,400 to 472.5 at 4,200 rpm. | 
The air/fuel ratio recorded by the Dynojet was a bit on the rich side, and we liked that. It held steady at 11.8:1. Just to be sure, we yanked the plugs, and they looked good. In the photo, they actually look a bit lean because of the effect of the camera flash. |