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.
4 The 347 stroker rotating...
4 The 347 stroker rotating assembly was stuffed inside a production 5.0L block machined and assembled by the experts at L&R Automotive. The two-bolt block was likely the weak point of the entire motor, but should survive plenty of bottles of nitrous.
5 Obviously our nitrous stroker...
5 Obviously our nitrous stroker deserved something better than a stock cam, so we installed an XFI stroker from Comp Cams. The XFI236HR-14 cam offered 0.579 lift, a 236/248-duration split, and a 114-degree LSA. Comp Cams also supplied the necessary hydraulic roller lifters, timing chain, and pushrods.
6 Sealing is an important...
6 Sealing is an important issue on nitrous motors, so we went right for the good stuff in the form of ARP head studs and Fel-Pro 1011-2 head gaskets.
7 Wanting to make serious...
7 Wanting to make serious power before hitting the button, we installed a set of Twisted Wedge Track heat 185 CNC- ported heads from Trick Flow Specialties.
8 As the name suggests, the...
8 As the name suggests, the Track Heat 185 heads feature 185cc intake ports capable of supporting over 600 hp (normally aspirated) thanks to flow numbers that just exceed 300 cfm.
9 Exhaust flow was equally...
9 Exhaust flow was equally impressive, as the Track Heat’s exhaust ports belted out as much as 231 cfm at 0.700 lift.
10 The Twisted Wedge heads...
10 The Twisted Wedge heads get their name from a unique valve orientation. The design both improves flow and increases piston-to-valve clearance.
11 To ensure adequate flow...
11 To ensure adequate flow to our 347 stroker, we installed a Holley SysteMax induction system. The upper and lower 5.0L intake not only flowed well, but produced power higher in the rev range (compared to the stock intake). It is critical to match the intake, heads, and cam timing for maximum power production.
12 Working with the Holley...
12 Working with the Holley Systemax induction system was a matching 75mm throttle body. Our stroker would certainly use all the airflow offered by the oversized throttle body.
13 The juice portion of our...
13 The juice portion of our fresh-squeezed stroker comes from Zex. The power offered by the universal wet EFI nitrous kit is adjustable thanks to a variety of different nitrous and fuel jets. We selected jetting to add 150 hp to our normally aspirated combination.
14 The nitrous fogger nozzle...
14 The nitrous fogger nozzle was positioned in front of the Holley throttle body using a radiused air horn.