If you recall from our November '08 issue ("A Monster is Born"), Steve Brulé of Westech Performance built a superb naturally aspirated 12:1 496ci big-block. We made good use of its internals too with a solid rotating assembly starting with a Lunati 4.125-inch stroker crank and 6.385-inch I-beam rods. The bores were then plugged with 48cc domed Wiseco pistons and topped with a heavy breathing pair of cylinder heads from AFR to create 12 points of compression. The AFR 325 as-cast lungs we installed flowed 385 cfm on the intake and 285 cfm on the exhaust at 0.700 inch of lift. At the center, we chose a high-lift Comp piece to deliver 274/280 intake/exhaust degrees of duration at 0.050 inch of lift and pulled out a matching set of solid roller Comp lifters. When all was said and done, we planted the mule on Westech's 902 SuperFlow dyno for testing. The bored and stroked combination churned out 780 hp and 658 lb-ft worth of stump-pulling force without even breaking a sweat.
Fast forward to the present and Brulé was itching for even more power to wring out of the Monster. When the phone rang he presented an idea we couldn't pass up-nitrous, and a whole lot of it, through Zex's Dominator flange nitrous perimeter plate system. What better way than to add more go without shelling out loads of cash. While some builders stay away from it, others like Brulé let it rain down in full force, literally. For the money, you can't deny the simple fact that a blast of nitrous through the intake plenum is the best instant power adder, hands down. When used safely, the amount of horsepower you get per dollar can't be matched by anything else out there. Plus, it's easily adaptable to most engine combinations. The added power from nitrous is obvious, but why is it so potent? To put it simply, nitrous oxide is laden with oxygen. When nitrous is fed down the intake, it's also mixed with extra fuel. By the time it reaches the combustion chamber and ignites with fuel from the carburetor, the extra oxygen from the nitrous is then released, creating massive cylinder pressure.
To prove Brulé wasn't all talk, we were back at Westech's facility to strap the 496ci back down and shoot it full of juice. To back up our previous findings we laid down a base run to 6,600 rpm in which case we were spot on at 779 hp. When Brulé pulled out the Zex perimeter plate, he wasn't messing around and loaded it up with the 250hp pills. How much was the nitrous worth on the dyno? Let's just say the visual chart doesn't do it justice; the beast leaped towards us and produced quadruple digit power figures-yes, it's that easy!
While there is more than one...
While there is more than one method for delivering nitrous to an engine, the plate system is easy and serves as a spacer that rests in between the mouth of the intake manifold and carburetor. Traditionally, a small, hollowed-out bar ran through the center of the nitrous plate. The nitrous and fuel solenoids would feed this bar and provide the engine with atomized fuel and nitrous. While this system is reliable, Zex took the idea a step further.
Westech's 496 big-block receives a Zex nitrous perimeter plate with a 250 shot
Bottom Line
We gain an extra 311 hp with a simple bolt-on and prove it on the dyno
Zex Jets
Precision-machined jets are used for adjusting both nitrous and fuel flow. They feature a special internal taper to minimize turbulence resulting in very consistent flow and power. Zex offers jets at $3.50 each.
Instead of a single bar spanning...
Instead of a single bar spanning the intake mouth, Zex surrounds the inside area of their plate with a perimeter design. Small outlets deliver an even flow of nitrous and fuel to the engine. Turbulence under the carburetor is all but eliminated while at the same time, creating a negative vacuum that "draws" even more air and fuel through the manifold.
Before our engine testing...
Before our engine testing began, we opened up the Zex plate for a testdrive. As nitrous is fed through the system, it's channeled throughout the plate evenly on all sides. This creates an almost fail-proof method of delivering the nitrous charge. When it's placed on the engine, the nitrous and fuel are essentially launched down each intake runner evenly.
What's great about a nitrous...
What's great about a nitrous system is the ability to bolt on the Zex plate kit and go without making any drastic changes; all we had to do was back down the timing. For example, we used the same intake manifold for the nitrous pulls as we did when it was naturally aspirated. Our Weiand Team G was able to supply the big-block with enough airflow to the AFR 325s.