When it comes to bang for the buck, nothing compares to nitrous oxide. Toss in the fact that it is easy to install (and conceal) and the power output is adjustable (as with forced induction). It’s easy to see why nitrous oxide is all the rage among street racers and enthusiasts. Short of a well-prepared turbo or blower, nothing runs harder than an LS engine on the juice.
Nitrous oxide offers a number of benefits, including the ability to adjust the available power level. Much like cranking up the boost pressure on a turbo, jet changes on a nitrous system allow you to literally dial in the extra power. However, there is a limit to the amount of nitrous that can be added, something usually dictated by the strength of the internal components and the original power output of the engine.
In addition to the adjustable power, street racers like nitrous because it can be easily hidden. Of course, it doesn’t take a genius to figure out that a stock 2010 Camaro was sporting something more than the stock when it knocks out consistent 11s at the track. Further improving upon the adjustable power and concealment is the cost. Compared on the basis of available power gains, nitrous offers far and away the best bang for the performance buck.
As you know, nitrous oxide is not a fuel, but rather it’s an oxidizer. Despite the automotive infernos depicted in movies such as The Fast and the Furious, nitrous oxide does not burn nor is it likely to incinerate a car. You could literally open the bottle of nitrous and touch a match to the spray and the only thing that would happen is that the match would go out. No thunderous explosions, no massive fire balls, just an anticlimactic wisp of smoke as the flame is extinguished by the high-pressure, ice-cold stream of nitrous oxide.
If nitrous oxide doesn’t burn, then how does it increase the power output of the engine? The answer is simple: Nitrous oxide adds power by releasing free oxygen molecules contained in the compound. Because oxygen molecules are a key ingredient in power production (the more oxygen present, the greater the power potential), the release of these oxygen molecules adds to the power potential of the engine. More nitrous equals more free oxygen molecules, which in turn equals more power.
Nothing wakes up an LS3 or LS7 application like a small shot of nitrous. Combine the right amount of nitrous and fuel through a single (or multiple) fogger nozzle(s) and you have instant horsepower.
There is, however, a limit to the amount of nitrous and the number of attending free oxygen molecules that can be added to any combination. While most stock engines, even those equipped with cast or hypereutectic pistons, withstand an increase of 40 to 50 percent (depending on the original power output and displacement), adding more power brings the strength of the internal components into play.
Building a high-horsepower nitrous engine is not much different than building a high-horsepower turbocharged or supercharged engine. Short-blocks typically include forged rods, cranks, and pistons, with MLS head gaskets, head studs, and possibly O-ringing the block. Nitrous and forced induction engines do, however, differ in their cam timing and cylinder head porting. Nitrous engines prefer big port volumes and a lot of exhaust flow because the nitrous adds all the necessary intake oxygen molecules. All those extra oxygen molecules must now be allowed to escape, thus the need for greater exhaust port flow and wilder exhaust cam timing.
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Adding power through nitrous is different than adding the same amount of power through forced induction. Sure, both add an easy 75, 100, or even 150 hp (or more) to an average LS engine, but how they add the power differs. Both forced induction and nitrous increase the amount of oxygen molecules available to produce power. Forced induction does so by increasing the mass flow of air. Pressurizing the air increases the mass flow, thus force-feeding the engine more air than it could ingest on its own or otherwise in NA form.
The unfortunate side effect of the pressurization of air (boost) is that the pressure causes heat. Turbochargers and superchargers heat the inlet air, something not desirable from either a power (less oxygen molecules per volume) or a detonation threshold standpoint. The hotter the air, the easier it is to ignite. In some cases, the heated inlet air can self-ignite before the spark plug initiates the burn. The result is an expansion of the air/fuel mixture while the piston is still on its way to TDC. As a result, the expanding gases resist the upward moving piston. The result of this struggle is sometimes not very pretty. The same thing can happen with excessive ignition advance.
Nitrous, on the other hand, does not resort to pressurizing the inlet air, but rather the extra oxygen molecules are carried in the pressurized compound. Once delivered to the inlet tract from a pressurized bottle, the liquid nitrous quickly turns into a gas. This liquid-to-gas vaporization requires an input of energy; in this case the energy is heat. The vaporization of the liquid nitrous absorbs heat from the surrounding inlet air, desirable in any performance application (especially a turbo or supercharged engine).
Although you associate heat with boiling (for example, water turning from a liquid to a gas), the vaporized nitrous does not produce heat (at least not to the inlet air). Although vaporized, the temperature of the nitrous oxide is still at or near minus 129 degrees F (the boiling point of nitrous oxide). Mixing the inlet air with a gas that is even that cold still provides a dramatic cooling effect. This double cooling reduces the chance of detonation and increases the density of the inlet air. Denser air equals more oxygen molecules, which in turn (potentially) creates more power.
Nitrous kits can be pretty elaborate but most feature the components illustrated in this NOS kit. The components include a bottle, solenoids, fogger or plate, jetting and arming, and activation switches.
Nitrous oxide (such as in this Zex kit) can also be used on carbureted LS applications with the Perimeter Plate system. This system was designed to evenly distribute the fuel and nitrous to all cylinders to maximize (safe) power.
Test 1: Modified LS3: NA vs Nitrous Using 100- and 150-hp Shots
The great thing about nitrous oxide is that it can be added to any engine, but big doses of nitrous are best used on modified engines designed to take the abuse. After all, nitrous kits can easily increase the power output of an NA engine by 100 hp or more.
This test was run on a modified LS3. Starting with a GM LS3 crate engine from Gandrud Chevrolet, the short-block was augmented with a set of CP forged, flat-top pistons and 6.125-inch connecting rods. The piston and rod upgrade were combined with the stock crank (more than strong enough for this level of nitrous). I retained the stock LS3 heads, but they were treated to a valvespring upgrade from BTR. Comp Cams supplied a 459 cam for this test that offered a.617/.624-inch lift split, 231/239-degree duration split, and 113-degree LSA. The stock heads were retained using Fel Pro MLS head gaskets and ARP head studs. This test relied on the stock LS3 intake, but I swapped on a manual 90-mm throttle body to replace the factory drive-by-wire unit. Run with long-tube headers, a Meziere electric water pump, and FAST XFI management system, the modified LS3 produced 552 hp, and 520 ft-lbs of torque.
To illustrate the power gains offered by nitrous oxide, I selected one of the affordable Sniper Kits from NOS. Because one of the ben- efi ts of nitrous is the ability to eas- ily increase power with a simple jet change, I decided to run two differ-ent power levels on this engine. The Sniped Universal EFI kit featured a 10-pound bottle, two solenoids, and a single fogger nozzle designed to inject the nitrous and fuel together. Because nitrous oxide is an oxidizer, extra fuel is a critical component to add to the extra oxygen molecules supplied by the compound. Using the supplied jetting, I set up the system to provide an extra 100 hp. Activat- ing the nitrous at 4,300 rpm resulted in a jump in power to 687 hp and 684 ft-lbs of torque. The Sniper system provided a nice, smooth power curve. After the success of the 100-hp shot, I stepped up to 150-hp jetting and was immediately rewarded with 732 hp and 730 ft-lbs of torque. I made sure to heat the bottle properly to ensure adequate bottle pressure prior to testing.
Because the stock valvesprings did not accept the available cam lift, I replaced them with a dual-valvespring upgrade from BTR.
In addition to forged rods and pistons, the LS3 also received a Comp 459 cam upgrade.
The Sniper universal wet EFI system offered plenty of bang for the buck. Applied to this modified LS3, the nitrous system increased the power output from 551 to 687 hp using the 100-hp jetting. This increased to 732 hp with the 150-hp jetting. Thanks to the forged internals from CP and Carillo, I felt confident adding this much power to the LS3.
The torque curves illustrate how easy it was to increase power on the nitrous-injected LS3. Simple by chang- ing jets on the Sniper system, I was able to increase torque production first from 520 ft-lbs to 684 ft-lbs, then up to 730 ft-lbs with the 150-hp jetting. Note the 300-rpm earlier activation (4,300 versus 4,600) on the 100-hp shot.
Test 2: 408 Hybrid Stroker: NA vs Zex Wet EFI Nitrous Using a 100-hp Shot
Aluminum LS3 engines are expensive and more dif- fi cult to come by than iron 6.0 truck blocks, and as a result, building your own 6.0 LS3 hybrid has become common practice. This works especially well if you bore and stroke the 6.0 to 408 ci as with this test engine.
The 6.0 iron block was fi rst bored .030 over then treated to a stroker assembly that included a Scat forged steel crank and 6.125-inch rods combined with JE forged (asymmetrical) pistons. Finishing the stroker was a Comp cam (PN 277LrHR13) that offered a .614/621-inch lift split, 227/235-degree duration split, and 113-degree LSA. Making this a hybrid was the fact that I topped off the .030-over iron block with a set of as-cast LS3 heads treated to a Comp beehive valvespring (PN 26918) upgrade. The engine was run with a stock LS3 intake, FAST injectors, and a Holley HP management system. As always, I replaced the drive-by-wire throttle body with a 90-mm manual version. Equipped as such, the NA LS3 hybrid produced 577 hp and 526 ft-lbs of torque.
After running the NA hybrid stroker, I installed the Zex Wet EFI nitrous kit. The cool thing about the Zex kit is that not only was it adjustable with different jet- ting, but the single fogger nozzle could be applied to just about any fuel-injected application. The kit included the purple 10-pound bot- tle, a digital controller, and a single fogger nozzle designed to combine the nitrous and fuel before injecting it into the engine.
After filling the bottle at West- ech Performance, I hooked up the system, went through the WOT learn procedure for the throttle position sensor (TPS), then purged the system. With plenty of bottle pressure, I activated the Zex nitrous at 4,500 rpm, and the power jumped immediately. It soon settled in with gains that exceeded 100 hp. Credit the extra power offered by the kit to tun-ing and bottle pressure above 1,000 psi. Increased bottle pressure works like a larger nitrous jet, and this Zex kit worked amazingly well on this hybrid stroker.
The test engine started as a 6.0, but the iron block was upgraded with a 4.0-inch SCAT stroker crank and K1 6.125-inch rods.
JE supplied the necessary forged flat-top pistons for the LS3-headed 6.0 stroker.
Nothing adds instant power like a good nitrous system. The Zex Wet EFI kit offered impressive power gain, upping the power output of the 408 hybrid stroker from 577 hp to 702 hp using 100-hp jetting. I did take the necessary steps to ensure proper nitrous pressure and delivery by preheating the bottle.
It is not unusual to see a massive torque gain on the initial activation of a nitrous system. The Zex kit added more than 200 ft-lbs to the stroker engine at 4,900 rpm but settled in to a more real- istic torque gain thereafter. Remember, the lower you activate the nitrous, the more torque you gain, but care must be taken not to become too greedy.
Test 3: Mild LS3: NA vs Nitrous Works Using a 100-hp Shot
I ran this test to illustrate that it is possible to not only add nitrous to any LS3 or LS7 combination (even a stock one), but do so safely. Forget the horror sto- ries and explosions shown on TV, movies, or YouTube, nitrous is not even flammable, nor does it hurt stock pistons or rods if tuned properly. Nitrous is simply an oxidizer that adds extra oxygen molecules. Extra oxygen means extra power, but the oxygen must have additional fuel to support the burn. Combine the two properly and inject into the engine and that’s when the magic starts to happen.
To illustrate how well nitrous companies have perfected their systems, I ran nitrous on an LS3 equipped with stock internals, meaning powdered-metal rods and cast pistons. The only upgrades made to the LS3 were a BTR cam and valvesprings. Run with headers, a Meziere electric water pump, and Holley HP management system, the cam-only LS3 produced 544 hp and 514 ft-lbs of torque. (See Chapter 3 for some serious cam-only information from BTR.).
As much as I love how well an LS3 responds to more aggressive cam timing, it responds even better to nitrous oxide. This includes an old, out-of-date system no longer available. Rummaging through the cabinets at Westech Performance, I ran across an old Nitrous Works kit from Barry Grant. No longer avail- able, the system was complete and ready to run. The Nitrous Works system included the usual array of solenoids, lines, and a single fogger nozzle, along with a 10-pound bottle, activation switch, and various hoses and fittings.
To test the system, I installed jetting to provide a 100-hp increase to the cam-only LS3. Despite not being available for some time, all the components worked well and the 100-hp jetting increased the power output of the LS3 from 544 to 660 hp. The torque gains were equally impressive; the nitrous increased torque production from 514 to 655 ft-lbs. Even on a near-stock engine, nitrous oxide works wonders.
The power output of the GM LS3 crate engine was increased by replacing the factory cam with a higher lift cam from BTR.
The cam swap necessitated replacement of the stock LS3 valvesprings. BTR supplied a set of double springs to accommodate the higher-lift and increased engine speed of the new cam.
Starting with a GM LS3 crate engine from Gandrud Chevrolet, I installed a mild BTR cam (and springs), then an old Barry Grant Nitrous system that I had laying around. Running jetting to supply an extra 100 hp, the single fog- ger system increased the power output of the mild LS3 from 554 hp to 660 hp. Nitrous offered nice, smooth, consistent gains.
Activation of the Nitrous Works nitrous system at 4,500 rpm resulted in impres- sive torque gains. I made sure to retard the timing by 4 degrees to eliminate any chance of detonation. Nitrous can transform a mild LS3 into a wild one with one push of the button.
Test 4: LS3-Headed 6.0L: NA vs Nitrous Using a 100-hp Shot
What is the next best thing to the LS3? Based on numbers alone, the obvious answer is an LS2, but this test engine offered an effective combination of both. Looking at the factory power ratings, the LS3 offered both more displacement and better head flow than the LS2, but that doesn’t mean an LS2 can’t make power like an LS3. All you have to do is replace the LS2 heads with the high-flow LS3 heads and intake manifold.
Although the swap can be performed on a stock short-block, this one was augmented with JE pistons and K1 rods (using the stock crank). Since the heads interchanged, the swap was easy, but replacing the LS2 heads with the LS3 heads required installation of the LS3 offset intake rockers and the LS3 intake manifold. The LS3 throttle body was also ditched in favor of a manual version and the 6.0 hybrid was run with a Holley HP EFI system, long-tube headers, and a Meziere electric water pump. Run with Lucas oil, the 6.0 stroker produced 493 hp and 461 ft-lbs of torque.
With a short-block at the ready, I decided it was plenty stout enough for some nitrous testing. For this 6.0/LS3 hybrid, I chose the NOS No Spray Bar Nitrous Plate system. Designed to sandwich between the throttle body and intake manifold, the system com-bined the fuel and nitrous to fi re it directly into the awaiting intake manifold. The system was adjust-able from 100 to 150 hp, but since the system employed Cheater sole-noids, optional jetting could take the system to 250 hp. For the 6.0 hybrid, I chose to stick with mild jetting to provide 100 hp. After installation of the system, I heated the bottle to get the pressure above 900 psi.
After pushing the activation button, the power output of the hybrid jumped from 493 hp and 461 ft-lbs of torque to 607 hp and 630 ft-lbs of torque. Any LS that pumps out more than 600 hp is a force to be reckoned with on the street.
The aluminum 6.0 LS2 block was equipped with LS3 heads to produce a hybrid. The build included JE forged pistons, K1 rods, and a stock crank. ARP head studs and Fel Pro MLS head gaskets were also used.
Tuning for the injected 6.0 LS3 came from a Holley Dominator. Dialing in both air/fuel and timing is critical when using nitrous. The Dominator was used to retard the ignition timing by 4 degrees with a 100-hp shot.
How do you not love a system that adds an easy 100 (or more) hp, regardless of what engine you are run- ning? Adding the NOS system to the LS3-headed 6.0 increased the power output from 493 to 607 hp.
Activating the NOS nitrous system at 4,000 rpm brought huge torque gains between 4,500 and 5,000 rpm. Because of the relationship between horsepower, torque, and RPM, simple math tells you that if you activate the system below 5,252 rpm, the torque gains will exceed the horsepower gains, meaning you will get consider- ably more than 100 ft-lbs if you add a 100-hp shot. The 100-hp shot on this LS3-headed 6.0 offered as much as 177 ft-lbs.
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Test 5: LS3 Stroker: NA vs Nitrous Using a 150-hp Shot
Things really get serious when you combine cubic inches and nitrous oxide. Case in point: this 417 stroker LS3. Starting with an aluminum LS3 block from Gan- drud Chevrolet, I installed a 4.0-inch forged-steel stroker crank and 6.125-inch connecting rods from Lunati. Completing the rotating assembly was a set of CP forged, flat-top pistons and Total Seal rings. The idea was to build a stout, NA combination to which I would add a healthy dose of nitrous. The 417 was completed using a set of CNC-ported L92 heads equipped with a dual-valvespring upgrade from BTR, as well as a camshaft for the stroker.
Designed for a 400-inch stroker, the BTR Cam offered a .631/.595-inch lift split, 251/266-degree duration split, and 112-degree +4 LSA. The engine was run with the stock LS3 intake, stock rockers, and Hooker long-tube headers using a Holley HP management system.
Before adding the NOS billet plate LS nitrous system, the engine was run in NA trim. As with any nitrous system, the power gains add to the existing output. In the case of this LS3 stroker, the engine produced 605 hp at 6,500 rpm and 542 ft-lbs of torque at 5,200 rpm. Torque pro- duction exceeded 500 ft-lbs from 4,300 rpm to 6,300 rpm, making for a broad power band.
The NOS billet plate system bolted between the 92-mm throt-tle body and factory intake mani- fold. The kit used jetting to adjust the power level, but the solenoids were capable of supporting more than 200 hp. I selected 150-hp jet-ting for this stroker and retarded the timing by 6 degrees before hitting the button. After activation of the nitrous, the peak power numbers jumped to 779 hp and 799 ft-lbs of torque. Credit the early engagement (4,500 rpm) for big-time torque gains. Run on nitrous, this stro- ker exceeded 750 hp over a broad range, meaning this would be a serious contender on the track (or street).
Starting with an LS3 block from Gandrud Chevrolet (GM Performance), I added a stroker assembly that included a forged Lunati crank, matching 6.125-inch rods, and CP Pistons.
The 417-inch LS3 stroker was topped with a set of GM CNC-ported L92 heads equipped with a BTR valvespring upgrade.
The Zex kit improved the power out- put substantially, adding 174 hp (peak to peak), and there were huge gains from 4,700 to 7,000 rpm. This nitrous-injected stroker offered one sweet power band, pulling strong all the way to 7,000 rpm. Talk about fun on the freeway!
Starting with more cubic inches and adding more nitrous is a surefire route to serious performance. This LS3 stroker offered more than 542 ft-lbs of torque, but the output jumped to 799 ft-lbs after activation of the Zex Perimeter Plate system.
Test 6: Stock LS3: NA vs Zex Nitrous Using a 200-hp Shot
As should be evident by the other tests in this chapter, it is possible to add nitrous to any combination, including a stone-stock LS3 (or LS7) application. To illustrate this fact, I added nitrous to a stock LS3 crate engine from Gandrud Chevrolet, and I added NITROUS. Why the caps, you ask? Because I added not some wimpy 75-, 100-, or even 125-hp shot, but a full 200 hp.
Although this may seem like a lot of juice for a stock engine to ingest, the reality is that a stock LS3 is a pretty impressive customer, offering nearly 500 hp on an engine dyno in the test configuration (headers, open exhaust, and no accessories). When you compare this 200-hp shot to the 493 hp offered by the LS3 crate engine, you see that even the big shot of nitrous represented a 40-percent increase in power. This was a lot of nitrous to add to an internally stock engine, but I took the neces- sary precautions before hitting the button and was rewarded with big power; and the LS3 was ready for more.
To prep for the test, I configured the injected LS3 crate engine with a set of Hooker long-tube LS headers and open exhaust, a Meziere electric water pump, and no air intake feeding the open 92-mm FAST throttle body (stock LS3 intake). Since tuning was critical on a stock engine with this much nitrous, I relied on a FAST XFI system to retard the required 8 degrees of timing upon activation and dial in the air/fuel mixture. As a hedge against detonation, I also filled the fuel tank with 114-octane Rocket Brand race fuel.
Before activation of the Zex single fogger system, I took the liberty of heating the bottle to produce optimum bottle pressure and nitrous flow. After purging the system, I activated the Zex kit on the LS3 crate engine and was rewarded with a jump in power from 493 to 706 hp. The torque gains were even more impressive because the peak grunt jumped from 484 to 737 ft-lbs. Every bit as important was the fact that the LS3 crate engine shrugged off the big hit and was ready for more testing.
The Zex kit run on the LS7 featured a controller that recognized the WOT voltage curve of the throttle position sensor (TPS) to ensure no nitrous would be delivered unless the engine was at WOT.
Bottle pressure is critical to maximize nitrous flow to the Zex con- troller. I used this pressure gauge with the bottle heater to ensure adequate pressure for each test run on the LS7.
These are the graphs I love to see when running nitrous. The power curve offered by the stock LS3 reached nearly 500 hp, but adding a 200-hp shot of Zex pushed the power output beyond 700 hp. Truth be told, a 200-hp shot on a stock engine might be excessive, but I ran this test on race fuel to eliminate any chance of detonation.
The torque curves were equally smooth, with huge gains offered below 5,000 rpm. Care must be taken not to activate the nitrous too early because excessive cylinder pressure can ruin a perfectly good engine. On the stock LS3, torque jumped from 484 to 737 ft-lbs.
Test 7: Cam-Only LS7: NA vs Nitrous Express Using 125- and 175-hp Shots
As the heavy hitter of the NA LS family, the LS7 has big shoes to fi ll. Sharing the name with a 12.0:1, rectangular-port, 454 crate engine (not offered in a production vehicle) meant that the modern LS7 better make some serious power. Luckily for LS enthusiasts, the modern 427 commands plenty of respect on the street and on the track.
What’s not to love about an all-aluminum LS engine offering 7.0 liters of displacement (427 ci), raised rectangular-port heads, and even a dry-sump oiling system? It took forced induction for the LSA and LS9 powerplants to eventually surpass the LS7 in terms of factory performance, but even the mighty big blocks of the muscle car didn’t make as much power as this modern 427. As good as the factory LS7 is, it can always make more power. In this case, more power came from a small shot of nitrous oxide.
Although the 427 LS7 is plenty powerful in stock trim, this engine was equipped with a mild Comp cam and valvespring upgrade. The mild cam helped it pro- duce just over 600 flywheel hp on the engine dyno. Run with the stock LS7 intake, Hooker headers and a Holley HP management system, the cam-only LS7 produced peak numbers of 602 hp and 557 ft-lbs of torque. While the cam peaked at 6,500 rpm, the LS7 pulled strong all the way to 7,000 rpm.
Like most systems, the Nitrous Express kit was adjustable using the supplied jetting. I heated the bottle once more until the pressure exceeded 900 psi, then let it rip with 125-hp jetting. The reward for proper preparation and tuning was a bunch of extra horsepower and torque. The peak numbers jumped to 726 hp and 641 ft-lbs of torque. Things escalated even fur- ther after I installed 175-hp jetting. This brought the totals to 784 hp and 721 ft-lbs of torque. The only thing better than an LS7 is one with nitrous.
Before I switched to the heated water tank to warm the nitrous bottle, I positioned it in front of this space heater (in retrospect, not a good idea, but I kept an eye on it).
The LS7 was upgraded with a mild cam from Comp Cams. The factory springs were also upgraded in the process.
As I often do when testing nitrous oxide on a combination, I ran this cam-only LS7 at different power levels. I started by adding a 125-hp shot then followed it with a slightly larger 175-hp shot. Because the LS7 featured stock rods and pistons, I limited the testing to 175 hp and ran the testing with 100-octane race fuel. Run in NA trim, the LS7 pro- duced 602 hp, but this jumped to 726 hp with the 125-hp jetting, then to 784 hp with the 175-hp jetting.
Equipped with the mild Comp cam, the 427 LS7 offered an impressive torque curve, but that curve picked up dramati- cally after I injected the nitrous. Successive steps in additional torque were offered by 125- and 175-hp jetting. All I did to achieve these power levels was change the jets. No wonder nitrous is so popular among racers, but don’t get greedy.
Test 8: 468 LS7 Stroker: NA vs NOS Nitrous Using a 250-hp Shot
Sometimes you just have to go big, and for this test going big meant both the engine and the amount of nitrous. A good rule is that the amount of nitrous you can add is a percentage of the original power output of the engine. The lower the percentage, the easier it is on the engine. Attempting to add 250 hp worth of nitrous to a 250-hp engine (100 percent) would be dif- fi cult, if not impossible because the mild engine might not be able to process that amount of nitrous. By contrast, adding that same amount of nitrous to an engine that already exceeds 750 hp means that you drop the percentage to a more manageable 33.
To determine if it was possible for a 750-hp com-bination to process an additional 33 percent power, I built just such a test engine. Starting with an aluminum LS6 block, the engine was treated to Darton sleeves, which allowed me to push the displacement to 468 ci, thanks to a stroker crank and large bore size. The stroker featured internal components from Lunati, CP, and Total Seal; induction chores were handled by Mast Black-Label heads and a matching single-plane (4500) intake manifold.
Even in NA trim, the LS7-based stroker was no slouch, thanks to a healthy Comp hydraulic-roller cam, a high-flow induction system, and a Holley 1050 Dominator carburetor. Run with an MSD ignition system, American Racing headers, and a Milodon oiling system, the carbureted 468 stroker produced 768 hp at 6,800 rpm and 658 ft-lbs of torque at 5,400 rpm. Torque pro- duction hovered near 650 ft-lbs for a solid 1,000 rpm and exceeded 600 ft-lbs from 4,250 rpm to 6,700 rpm.
Obviously, I had a good start to making power, but things became serious once I added the extra 250 hp from the NOS carbureted (cheater) plate kit. With adjustable jetting, I set up the system to add a solid 250 hp, which I hoped would push the stroker over the 1,000-hp mark. After activation, the power needle jumped to 1,006 hp and pushed the torque output to 951 ft-lbs. Peak power exceeded 1,060 hp at the spike, but I selected a number over 1,000 hp after the power curve settled in. Four-digit LS engines don’t grow on trees, but the right combination of displacement and nitrous can make serious power.
The 468 stroker was equipped with a set of Mast Black-Label LS7 heads. The Darton-sleeved LS6 block also featured a Lunati crank and rods combined with CP Pistons.
A Holley 1050 Dominator and NOS plate nitrous system topped the Mast two-piece single-plane intake. The Mast intake also featured provisions for injectors, but these were simply plugged during the test.
Not counting the big gain after activation, the 250-hp shot added almost exactly that. Had I not run out of nitrous during the run, the gains would have been consistent to 7,000 rpm. Regard- less, the NOS kit added some serious power to an already impressive LS7 stroker combination. Initially in the run, the NOS-equipped LS7 spiked to well over 1,000 hp and then settled to 1,000 hp. Any engine that cracks the 1,000-hp mark is a serious player indeed.
As I have come to expect, I had a huge jump in torque after the initial activation, but because I activated it after 5,252 rpm, the torque gains diminished with engine speed. The fall off at the top of the rev range was the bottle running low on nitrous. Even on a serious 468 LS7 stroker, you can feel an extra 300 ft-lbs of torque!
Written by Richard Holdener and republished with permission of CarTech Inc
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