Richard Holdener
September 1, 2009
Probe Racing supplied a set of forged flat-top pistons. The flat-top design usually produces a less-than-street-friendly static compression ratio on these large-displacement motors, but we combined the flat-top pistons with large (70cc) combustion chambers to produce a pump-gas friendly ratio of 10.2:1.

With both displacement and compression taken care of, we turned to cam timing. When it comes to cam timing, the real choice is driveability versus power. Wilder cam timing (high-lift and long-duration) will result in higher peak power numbers and usually elevated power numbers higher in the rev range, but the cost is almost always low-speed torque production. The wilder the cam timing, the longer (in rpms) it takes for the motor to come on the cam and become efficient. The net result is lackluster performance lower in the rev range. Sure, the motor pulls like a freight train on the big end, but down low, it won't pull the sprouts off a Chia Pet. Obviously, compromise is in order when choosing a cam for a street motor, but our choice may surprise some. Rather than go with the typical hydraulic roller, we chose a solid roller profile. Not only did we choose a solid roller, but we chose one from Comp Cams that offered super aggressive ramp rates. The ramp rates were designed to maximize power production throughout the rev range-a feature definitely valuable on a street motor. Besides, the TK-series cam in question was actually leftover from my Engine Masters entry. Despite being a solid roller with aggressive ramp rates, the cam profile was designed to optimize power production below 6,800 rpm. The TK-series roller cam offered 0.688 lift (both intake and exhaust), a 249/253-degree duration split (at 0.050) and a lobe separation of 109 degrees. Though a high-lift, solid roller, this TK-series cam was smaller (in specs) than the largest XFI stroker hydraulic roller cam offered by Comp Cams (a popular choice for stroker Ford combinations).

Wanting to maximize average power production, we selected a solid-roller cam. The TK-series cam offered 0.688 lift and a 249/253-degreed duration split (at 0.050). A leftover from Engine Masters Competition, the cam was sized to offer plenty of power below 7,000 rpm.

One of the key ingredients in the power production of any motor is cylinder head flow. Working with the cam timing and intake design, the head flow helps dictate both how much (and where) in the rev range the motor makes power. Knowing that our large-displacement combination was going to need some head flow, we chose a set of CNC-ported Trick Flow Specialties' High-Port heads. The head choice was actually reason number two for my excitement with this build up, as the original TFS/KPI High-Port heads were my first venture into the world of performance aluminum heads for the 5.0L Ford (and Windsor applications).

While those original High-Port heads certainly offered a sizable jump in power over the factory E7TE Ford 5.0L castings, these fully ported versions from Trick Flow represented a giant leap in both technology and performance over the originals. Thanks to a combination of the 2.08/1.60 valves, CNC-porting, and careful hand blending, the Trick Flow High-Port heads offered impressive flow figures. The 225cc intake ports offered 335 cfm at 0.700 lift, while the exhaust flow checked in at 258 cfm at the same valve lift. These flow numbers at 0.700 lift were relevant since our TK-series cam offered 0.688 lift on both the intake and exhaust. The heads were set up with valvesprings to accommodate our near 0.700-lift roller cam and titanium retainers.