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Comp Cams Install - Stroker Cam Comparo
XFI stroker cam test: Real power or real B.S.?
When it comes to extracting every last ounce of horsepower from your combination, look no further than your camshaft. The cam is the heart and soul of any performance motor, and the right profile can literally make or break your power curve. The 5-liter Mustang has been around for over 20 years, and the same basic engine (in non-roller form) has been with us since before the inception of the Mustang in 1964.
With so much time to develop cam profiles for one particular V-8, could there possibly be anything new under the sun for the 5-liter Mustang? Well, Comp Cams thinks so. It has come up with a series of trick profiles designed specifically for fuel-injected applications. Truth be told, though the new XFI profiles were designed with EFI motors in mind, this test was run on a carbureted motor with excellent results. Part of the reason for the success of the XFI profile on this test can be attributed to the fact that this profile was designed specifically for large-displacement stroker applications.
What exactly is a stroker cam? According to Comp Cams' lead cam designer, Billy Godbold, "The piston velocity in an enlarged stroke engine is greatly increased, resulting in an intake charge event which continues even past the point of Bottom Dead Center (BDC)."
What this means is that the long stroke increases the acceleration rate of the piston down the bore (relative to a shorter stroke). The draw on the intake charge from a stroker motor is so strong that cylinder filling actually continues to take place past bottom dead center. The XFI intake cam profiles feature late intake closing points to take full advantage of the extra filling offered near the end of the intake stroke. In addition, the exhaust valve is opened earlier to help reduce some of the pumping losses associated with the increased stroke.
Basically, all this technical mumbo jumbo means that the XFI stroker cam profile is designed to work harmoniously with the increased piston speed to optimize cylinder filling. As we all know, more cylinder filling equals more power. More power equals a big smile on the face of a Mustang owner.
To illustrate the benefits offered by the new XFI stroker cam profiles, we installed a 408 stroker supplied by Coast High Performance on the engine dyno and subjected it to a cam swap. The stroker motor was first equipped with an Xtreme Energy profile that offered a 230/236 duration split, 0.545/0.565 lift and a 112-degree lobe separation. The CHP 408 featured the AFR 205 heads used in a recent head test, an Edelbrock Super Victor intake and a Barry Grant 850 Mighty Demon carb.
With Hooker headers and an MSD ignition, the 10.0:1 408 produced 521 hp and 509 lb-ft of torque, making it an ideal candidate for a performance street Stang. After running the Xtreme Energy cam, we installed the XFI stroker cam profile.
The XFI cam offered 0.579 lift (both intake and exhaust) and a 236/248 duration split. The lobe separation was increased to 114 degrees. Equipped with the XFI cam, the 408 stroker produced 549 hp and 517 lb-ft of torque, clearly showing its superiority. Every bit as impressive was that the XFI cam didn't trade much power even down as low as 3,000 rpm for the impressive gains past 5,000 rpm.
Comp XE vs. XFI Cam Test-CHP 408 Stroker
As Evident by the graph, the larger XFI cam profile really showed its worth on this 408 stroker assembly. Specifically ground to match the increased piston speed and specific cylinder filling needs of a large-displacement stroker assembly, the XFI cam improved the power output of the 408 from 521 hp to 549 hp. The increase in power past 5,000 rpm came with little or no power loss all the way down to 3,000 rpm. Obviously, all the research and development that went into the new cam profiles was time well spent. Note that the XFI cam not only improved the peak power output, but also improved the peak torque production, raising it from 509 lb-ft at 5,000 rpm to 517 lb-ft at 5,100. That the torque peak occurred just 100 rpm higher in the rev range is an indication there was more than the extra duration offered by the XFI cam at work here.