It Takes Two: Dual Zex LSX

The only thing better than one nitrous kit is….well, you get the idea.

The only thing better than one nitrous kit is….well, you get the idea.

Words and Photos By: Richard Holdener

What can we say, sometimes you just want to go BIG! What do we mean by big? The philosophy of going big is simple. It states that if one nitrous kit is good, two must be even better. Now, while it is possible to run two nitrous kits (or stages) on a single four-barrel intake, we decided that going big for us also meant two carburetors. After all, if one carburetor is good, then two must be…well, you get the idea.

Truth be told, this all started the last time we ran a dual-quad, tunnel ram and noticed how convenient it would be to simply add not one, but a pair of plate nitrous systems to the combination. Nitrous fans will be quick to point out that it is possible to get the same amount of power from a single system, but they would be missing the point. It is possible to make plenty of power from a single turbo system, but twin turbo sounds so much better (and badder). Having a blower sticking out of the hood is always good, but what if you had a centrifugal supercharger or turbo feeding that blower? Now, you are starting to get the idea.

Given the power potential of even mild jetting on a pair of plate systems, we needed a suitable test motor capable of withstanding the extra cylinder pressure. Lucky for us, we had just such a motor sitting around just begging to be used. Nicknamed the Magnificent LS7, the 427 LSX was plenty stout thanks to the serious components used in the original build up.

The 7.0L stroker started out life as a simple LSX block from Gandrud Chevrolet. After machining, the iron race block was treated to forged internals that included a Lunati Voodoo crank, Bullet-series CP (flat-top) pistons, and matching Carrillo rods. Stepping up with the cam for the LS7 was Brian Tooley Racing. Originally designed for an LS7-headed application, the Stage IV grind featured a .616/.595 lift split (with 1.7 rockers), a 247/258-degree duration split, and 112+3. COMP Cams also stepped up in a big way with hydraulic roller lifters, hardened pushrods, and a trick, aluminum front timing cover. Given the power gains involved with nitrous, we made sure to include ARP head studs and Fel Pro MLS head gaskets in the build.

A stout short block is all good, but there were plenty of additional components used on the 427, like the complete Moroso oiling system. The Moroso components included a dedicated pan, pick up, and windage tray, along with a remote oil filter that ensured adequate delivery of the Lucas 5W-20 oil from the HV oil pump. Finishing off the short block was an ATI Super Damper, while the induction system consisted of Gen X 245 heads from TFS topped by a dual-quad, Holley Hi Ram. Using the dual-quad top on the Hi Ram allowed us to mount a pair of the Zex Perimeter Plates.

Continuing with the overkill theme was a pair of Holley 950 Ultra XPs. Sure, one would probably be more than sufficient at this power level, but why stop at just one? Holley also supplied the dual-quad throttle linkage, while MSD came through with their ignition controller, allowing us to dial in the timing curves for each combination (including retarding the timing for the nitrous). Finishing touches included a set of stock (LS1) rockers, 1 7/8-inch Hooker headers and a Meziere electric water pump.

Like most carbureted nitrous systems, the Zex Perimeter Plates were designed to sandwich between the carburetor and intake manifold. According to Zex, the Perimeter Plate system offered a number of other design features, including Perimeter Injection, Cryo-Sync, and Airflow Enhancement technology. The Perimeter Injection employed 24 injection points that combined nitrous and fuel to optimize atomization and distribution in the manifold. Flowing super cool nitrous (-127 degrees) through the plate effectively turned it into a Cryo-Sync (or heat isolator) to help cool the intake and carburetor. Flow of the nitrous and fuel through the plate and into the manifold also created a low-pressure zone to further enhance airflow into the motor. On paper at least, each Perimeter Plate sounded pretty effective, so we decided to install the dual kit on our 427.

Using jetting to control the nitrous and fuel flow, the Zex Dual Perimeter Plate system was adjustable from 100 to 300 hp. For this 427 LSX test, we chose to run the system at 200 hp (100 hp per plate). This was a reasonable amount for street use, especially when adhering to the recommended timing retard for this power level. According to Zex, the timing should be retarded by four degrees for each 100-hp shot, or a total of eight degrees for our dual system. To hedge our bets, we mixed in some race fuel just to be safe — we have a lot more testing in store for the LSX.

427 LSX-NA vs Zex Nitrous-(200-hp Shot) Nothing wakes up a motor like a little shot of juice. Adding the dual-plate nitrous system from Zex to the carbureted 427 LSX offered substantial power gains. Thanks to Perimeter Plate technology, the kit improved the power output of the LS stroker from 661 hp and 589 lb-ft of torque to 877 hp and 825 lb-ft. These were actually the spike numbers that occurred upon activation, but the power output increased by a nice solid 200 hp through the entire curve. Whether your combination is injected or carbureted, nitrous is flat-out awesome!

427 LSX-NA vs Zex Nitrous-(200-hp Shot)
Nothing wakes up a motor like a little shot of juice. Adding the dual-plate nitrous system from Zex to the carbureted 427 LSX offered substantial power gains. Thanks to Perimeter Plate technology, the kit improved the power output of the LS stroker from 661 hp and 589 lb-ft of torque to 877 hp and 825 lb-ft. These were actually the spike numbers that occurred upon activation, but the power output increased by a nice solid 200 hp through the entire curve. Whether your combination is injected or carbureted, nitrous is flat-out awesome!

Each nitrous and fuel solenoid fed a T-fitting that supplied nitrous (or fuel) to the pair of plates. We hooked up a simple activation button on the throttle handle in the dyno control room and made sure to activate only at WOT. We also took the liberty of heating the bottle to ensure adequate bottle pressure before activation. Run in normally aspirated trim, the tunnel-rammed 427 produced 661 hp at 6,700 rpm and 589 lb-ft at 5,200 rpm. After activation of the dual Zex system, the peak numbers jumped initially to 877 hp and 825 lb-ft of torque, but eventually settled in with a solid 200 hp gain through the tested rpm range. I guess when it comes to running Zex on an LSX, twice is nice!

Sources: ATI, Atiracing.com; ARP, Arp-bolts.com; Brian Tooley Racing, Briantooleyracing.com; COMP Cams, compcams.com; CP Pistons/Carillo Rods, Cp-carillo.com; FAST, fuelairspark.com; Gandrud Chevrolet, [email protected]; Holley/Hooker/NOS, holley.com; Lunati, Lunatipower.com; Moroso, Moroso.com; Total Seal Rings, Totalseal.com; Trick Flow Specialties, trickflow.com; Zex, zex.com.

About the author

PPN Editor

Power & Performance News is the source for news, tech and products that help you get more performance from your vehicle. If powertrain performance projects and hardcore technical content are your interest, Power & Performance News is the publication designed for you. Our acclaimed editorial staff covers all aspects of engine and driveline upgrades with a mission of presenting information that is both interesting and achievable for the “average car guy”.
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