Richard Holdener
May 3, 2011

To illustrate the gains offered by a good nitrous kit, we set up a test on the engine dyno using a typical 347 stroker. The idea was to build a suitable test motor, then subject it to a healthy dose of squeeze. With high horsepower in mind, we stuffed a stock block with a forged stroker crank and 5.4-inch rods from ProComp Motorsports, and forged slugs from Probe Racing, as well as a Speed Pro ring package designed to maximize sealing under harsh conditions.

Topping the 347 is a set of Twisted Wedge Track Heat 185 heads from Trick Flow Specialties, a Comp XFI Stroker cam from Comp Cams, and a Holley SysteMax upper and lower intake system, including a 75mm throttle body. Additional components included a set of Hooker long-tube headers, Meziere electric water pump, and ProComp Motorsprots 28-ounce damper. This 347 stroker was machined and assembled by L&R Automotive. For tuning, we relied on a FAST management system and 36-lb/hr injectors. Prior to running, the motor was treated to Lucas break-in oil and a pair of break-in cycles.

Once tuned, the 347 stroker produced 463 hp and 343 lb-ft of torque, with torque production exceeding 400 lb-ft from below 3,500 rpm to 6,000 rpm. Waiting in the wings was our Zex wet EFI nitrous kit, with a jetting set to provide an extra 150 hp. We made sure to warm the bottle to optimize the bottle pressure (above 900 psi), and once activated, the peak numbers jumped to 617 hp and 616 lb-ft of torque. That is serious power at the push of a button, and though the Zex kit can be configured to provide even more, concern for the strength of the production 5.0L block kept us from further squeezing. Once activated, the peak numbers jumped to 617 hp and 616 lb-ft of torque.

Fresh Squeezed 347-NA vs. Zex Nitrous

The graph illustrates that the 347 stroker was a healthy combination to start with, but really got with the program once we pressed the fun button. In normally aspirated trim, the 347 produced 463 hp and 434 lb-ft of torque, but these numbers jumped to an amazing 617 hp and a like amount of peak torque once the Zex nitrous kicked in. Given the power offered by the normally aspirated combination, we wouldn't think twice about running a 175hp shot, but we have some concern for the stock block at those elevated power levels.

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