ON THE BRINK, PART 1

PUSHING A STOCK BOTTOM END 6.7L POWER STROKE BEYOND 800-RWHP

We’re on dangerous ground. We’ve crossed paths with the owner of a bone-stock, 5,000-mile ’17 Super Duty Platinum who’s not afraid to slip the trans, bend a few rods, or even window the block. It’s right where we like to be: on the edge and pushing the limits. While there are some definite do’s and don’ts associated with all ’11-‘19 6.7L Power Strokes, the definitive red line on horsepower is yet to be drawn— especially with the newest engines. With bigger wrist pins introduced in ‘15 and then larger rods infiltrating the 6.7L V-8’s crankcase in Job 2 ’17 versions, the end-all, be-all amount of power one of them (and which one of them) can take is hard to know for sure. Some have shelled between 650 and 700-rwhp, and some have hung in there at nearly 750-rwhp.

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Although we don’t plan to scatter the 6.7L Power Stroke in our guinea pig, we do plan to push the truck past the 800-rwhp mark with as few upgrades as possible. Helping us reach our fueling goals, Exergy Performance supplied one of its 10mm CP4.2 high-pressure fuel pumps and a set of 60-percent over injectors. With Exergy’s stroker CP4.2 being capable of supporting 800-rwhp and its 60- percent injectors capable of supporting well north of that, it will be interesting to see what kind of fuel-only numbers we can squeeze through this alumi-duty. If the 6R140 plays ball and we meet our horsepower goal on fuel, we may plumb in some giggle gas and try to squeeze a four-digit figure through the factory automatic. Think we can do it? We’ve been told it’s not possible—so now we have to at least try…

Stay tuned for Part 2. This project is bound to either produce an impressive dyno graph or a few fireworks.

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Barely out of its first oil change, our 5,800-mile test-mule is about as fresh as it gets. The ’17 F-350 Platinum certainly looks the part, thanks to a 3.5-inch lift from ReadyLift and 35-inch Toyo Open Country M/T’s mounted on 22×12 Fuel Forged FF19 wheels, but now it’s time to match its appearance with some serious firepower. Will the 6.7L Power Stroke survive the 100-percent increase in horsepower and torque it’s about to see?

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Graced with a cam that provides 10mm of stroke, Exergy Performance’s upgraded CP4.2 for the 6.7L Power Stroke flows over 30-percent more fuel than the factory ’17 Bosch CP4.2 pump can. The added displacement of the Exergy stroker pump facilitates its ability to support up to 800-rwhp. It retails $2,300 and requires no core, which makes it an affordable, bolt-on upgrade for the enthusiast looking to pair it with a mild injector nozzle upgrade.

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While Exergy’s stroker CP4.2 is rated to support up to 800-rwhp, the company’s 60-percent over injectors can support much more. Needless to say, it will be interesting to see what kind of fuel-only numbers we can squeeze through our F-350. If the 6R140 will hold, we don’t think 850 to 900-rwhp is out of the question.

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Following a baseline and function test on the low-mile injectors we sent to Exergy, they got to work cleaning and prepping them for modification. After that, abrasive flow machining was employed to make each nozzle’s overall flow 60-percent higher than stock. Along with the work performed on the nozzle, the Piezo actuator and select other internals were modified within each injector body. Retail for a set of Exergy’s 60-percent over injectors is $4,315.60.

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Proven and validated, every set of injectors Exergy builds comes with a detailed flow sheet displaying the calibration results. In the case of our 60-percent over injectors, their output was balanced to within 4-percent of one another. In a max effort scenario, each injector is capable of flowing approximately 320 mm3 at 2,000 microseconds of duration and 180 Mpa (26,100 psi) of rail pressure.

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As each factory injector came out of its respective head, it was labeled according to the cylinder number it resided above. This important tracking measure was necessary because without taking it we would’ve had to change the IQA (Injector Quality Adjustment) codes once the injectors were sent back to us. Altering IQA codes can only be done by reprogramming the PCM. To label each unit, we simply engraved its number at the top of the body.

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Though accessing the injectors and CP4.2 on a 6.7L Power Stroke is quite involved, everything on our 5,800-mile Super Duty came apart without a fight. Once the factory air intake, intercooler piping, and upper and lower intake plenums were out of the way, the injectors, high-pressure fuel lines, and pump were removed relatively quickly.

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When the Exergy stroker pump arrived, we set to work removing the factory CP4.2. The process required removal of the fan shroud and fan, followed by the serpentine belt and even the belt tensioner.

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Gaining adequate room to access the pump’s drive gear nut also required that the fan hub assembly be pulled. After that, the vacuum pump was removed from the engine and set aside, and the CP4.2 drive gear nut was broken free.

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On the 6.7L Power Stroke, the CP4.2 is timed to both the crankshaft and camshaft, and its drive gear is directly driven by the camshaft gear. To keep the pump in perfect time, the timing mark on the cam gear must sit between the two timing reference marks present on the pump’s drive gear.

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With the CP4.2’s drive gear removed, the pump’s three mounting nuts were broken loose. Then the factory CP4.2 was finagled free from the front cover, maneuvered off of its respective mounting studs, and hoisted out of the valley.

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Using a new rag and brake cleaner, both the pump gear and the exposed portion of the stroker pump’s camshaft were thoroughly cleaned. After that, the O-ring on the CP4.2’s cam bearing housing was lubricated with a coat of fresh engine oil.

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From there, the pump was set in place on its three mounting studs and pushed forward against the back of the front cover. Once it was flush with the front cover, the mounting nuts were reinstalled and torqued to 89 in-lb. The pump’s drive gear nut was then torqued to the recommended 59 ft-lb.

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Moving on to the injector installation, the injectors were laid out just as they would be installed in each bank. Also notice the high-pressure lines on the left. It’s always wise to heed FoMoCo’s advice when reassembling a 6.7L Power Stroke injection system and start with brand-new lines.

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It goes without saying that brand-new O-rings were installed on the injectors as well. Note that the only O-ring on the body installs in the upper notch of the two shown here, not the bottom one nearest the nozzle. Each injector body O-ring was treated to fresh engine oil before installation. New return O-rings and stepped copper gaskets were installed, too.

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Inserting the 6.7L’s injectors into the cylinder heads is made relatively simple thanks to the injector hold-down clamps. Each one features a taper that effectively self-centers it (and the injector) within the injector bore.

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Not wanting to take a chance on a freak occurrence such as an injector hold down bolt backing out, a portion of each (brand-new) fastener’s threads was bathed in ARP’s Ultra-Torque assembly lubricant. Use of ARP’s Ultra-Torque gave us peace of mind in knowing that the most accurate preload was achieved.

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Each injector hold-down clamp bolt was threaded in and torqued to 22 ft-lb. Then, per Ford’s instruction, they were turned another 90 degrees. This is precisely why the aforementioned ARP Ultra-Torque assembly lubricant was used on these fasteners.

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Using a 12-point, 17mm injection line socket, the new high-pressure fuel lines spanning from the rails to each injectors were installed. The dual torque sequence called for 177 in-lb on the first pass, and 26 ft-lb on the second.

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With the rail to injector supply lines installed, the return lines were snapped into place on the injectors. Then the injector harnesses were plugged back in. Given the fact that a second turbocharger would soon be sitting under the hood, we also took care to make sure all lines were as close as possible to the valve cover.

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Next, the high-pressure lines that route fuel from the CP4.2 to the rails were cleaned out using compressed air and then reinstalled. At the pump, the fittings were torqued to 30 ft-lb. At the rails, they were tightened to 26 ft-lb.

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After that, the factory fuel filter reservoir and all of its corresponding lines were reinstalled. For good measure, a fresh secondary Motorcraft fuel filter was also installed (one of two filters included in PN FD4625).

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With the injection system buttoned up, we taped off all open ports while we await the arrival of the new turbo system. By the end of Part 2, the Super Duty’s engine bay will look considerably different, with an 82mm atmosphere charger perched atop the passenger side valve cover and an upgraded VGT in the valley. Stay tuned!