Muscle Mustangs & Fast FordsHow To Engine
Procomp Electronics IR Intake - Stack Attack
Individual Runner Intake Test
When Ford introduced the factory fuelie engine in 1986, it ushered in a new era of performance. Much has changed since the injected 5.0L H.O. first hit the streets, but the popularity of the small-block Ford has not diminished. The 5.0L is a favorite among Mustang owners, but is favored in swap applications, including Cobra replicas. While it is hard to argue with the performance and reliability of the factory (or the many aftermarket) fuel-injected intake systems, most have one thing in common—a single throttle body.
As effective as they are, they (like their single four-barrel carbureted counterpart), lack a certain sex appeal. For some, show is every bit as important as go and nothing screams “look at me” quite like an individual runner (eight-stack) injection system. When it comes to eye-popping induction, if one throttle body is good, eight is even better!
Individual-runner (IR) intake manifolds are not exactly new, having been run successfully on the Shelby Cobras back in the ‘60s. Those systems featured a quartet of Weber downdraft carburetors, but modern systems have replicated the look of the original systems, while upgrading them with versatility of EFI. The application of modern electronic fuel injection to replace the Weber carburetors has eliminated one of the major problems associated with the eight-stack system—namely precise fuel metering.
Properly tuned, the Webers would often provide decent idle quality or maximum (safe) power, but almost never both. This was especially true of engine combinations that include aggressive cam timing, as the carburetors simply could not provide precise fuel metering through the entire rev or load range. Obviously, stand-alone EFI cured this problem, but it created a few others along the way.
When it comes to individual-runner injection, the major concerns include synchronized throttle opening, proper manifold absolute pressure (MAP) signal, and pricing. According to Procomp Electronics, its new IR intake system has addressed all three concerns. While not cheap, the system sells for $3,499. That includes the lower intake, throttle bodies, polished stacks, throttle linkage, fittings, stand alone ECU, wiring harness, all sensors, injectors, fuel rails, adjustable fuel pressure regulator, fuel filter, distributor, and gaskets.
With systems designed for both 302 and 351W applications, the new induction features precision throttle-blade machining and a centrally located (bell crank) throttle to minimize the deflection inherent in unequal-length, crossover rods. The MAP signal was strengthened with the use of a common plenum machined into the bottom of the intake manifold. Rather than receiving an erratic signal from a single runner (which plays havoc on idle quality and drivability), the common plenum provides a balanced vacuum signal supplied evenly by every intake port. In terms of pricing, reduced labor costs and impressive buying power combine to keep the retail cost of this system from Procomp Electronics well below competitive systems. Concerned that price and performance often go hand in hand, we decided to put one of the new 351W systems to the test on a 408 stroker.
The Ford Windsor stroker was upgraded to 408 status courtesy of a 0.030 overbore and the addition of a 4.0-inch stroker kit from Scat. The Scat components included a 4.0-inch forged-steel stroker crank and 6.0-inch forged-steel rods. The crank and rods were combined with JE forged pistons. The dished pistons kept the static compression ratio in the streetable range (9.5:1) when combined with the 60cc chamber on the CNC-ported KC LH F 17 Brodix heads.
Some may question our choice of the smaller 195cc intake ports (the KLH 17 heads were available with 210cc intake ports) for our 408 street stroker, but how do you argue with nearly 300 cfm? Big flow through smaller ports is a one-way ticket to performance, and improved part-throttle driveability and mileage. The aluminum heads featured 17-degree valve angles, a 2.02/1.60 stainless steel valve package, and full CNC porting. The Brodix aluminum heads were secured using Fel Pro 1011-2 head gaskets and 1⁄2-inch ARP head studs. ARP also supplied a number of other fasteners, including a balancer bolt, oil pan studs, and an HD oil pump drive.