We decided to reuse the Comp Cams NX268 cam, 1.5 stamped rockers, and the stock heads since they survived the first flogging unscathed, as did the single-plane intake and Demon 750-cfm carburetor. From our prior experience, we figured the original dual-stage 450hp Nitrousworks kit we used the first time around would still be enough. If need be, we could always step up to one of Nitrousworks' Magnum "X" Dual Stage Systems. This system can flow up to 550 hp on the second stage, which suited us just fine.
Nuke DayAfter taking out a Westech Fragmentation Insurance policy and outfitting dyno operator Steve Brule with a Car Craft signature flak jacket, we were ready to rock 'n' roll. After talking to Steve about our last nitrous romp, we decided we would not purge the system, allowing the fuel to reach the intake and the cylinders first, creating a few nanoseconds of rich mixture that might keep our Mouse motor alive a little longer. Steve told us about research that Westech had seen using a Motech EFI system with a purged nitrous system that reportedly saw the nitrous reach the cylinder first that generated 15:1 air-fuel ratios for about 0.200 second before dropping down to a much safer ratio.
Like last time, we started with a few normally aspirated runs to establish a baseline power level. We also wanted to see if the new pistons and rings helped the horsepower since everything else was essentially the same. The rebuild was worth only a couple of ponies with the normally aspirated pulls making 330 hp at 5,600 rpm and 350 lb-ft of torque at 4,200. Keep in mind that this is with untouched stock iron castings with the Comp Cams 268 Xtreme nitrous cam, a Victor Jr. single-plane, and a Demon 750-cfm carb all running on 91-octane pump gas using an MSD 7 box and the coldest plugs we could find. We skipped over the 100hp shot and went right to the 200hp combo. The little motor thumped up to 510 hp at 5,200 rpm and an amazing 572 lb-ft of torque. That's when we decided to get greedy.
We loaded up the big pill package and cinched our steel helmets on tight. Charitable folks that we are, we felt a tinge of guilt creep in right before we fired the engine, so we decreed to the assembled throng in the dyno cell that if the small-block survived this run that we'd spare its life. After all, here was our trooper Mouse motor with its head firmly secured in the dyno cell guillotine and Steve the hatchet man poised with the button clenched in his fist. Steve ran the engine up, hit the button, and a flame the size of the Empire State Building shot up to the ceiling of the dyno cell, impacting melted aluminum from the carb's boosters on the ceiling! Clearly, our shot went dead lean, but amazingly the carb and engine survived, even if the bottom of the boosters were slightly melted.
At this point, we'll spare you the agonizing details of how we discovered that we had reached the saturation point with the nitrous. We were trying to shove 10 pounds of nitrous through a 2-pound engine bag, and it just wasn't going to work. As we eventually discovered, our stock little small-block could only breathe in a given amount of nitrous. As best we can figure, the load the engine had to exhaust didn't all make it out of the combustion chamber before it was time for the next load of nitrous to enter. The intake valve would open, and as Steve said, "It's like the intake manifold became another combustion chamber." That's when we'd see the flame shoot out the intake.