WHY THE 6.7L POWER STROKE IS SO GREAT

…And the Aftermarket Parts That Make It Even Better

In bringing CGI block technology, reverse-flow cylinder heads, air-to-water intercooling, 400 hp and 800 lb-ft of torque to the diesel truck segment, Ford’s 6.7L Power Stroke was big news. Since its release in 2011, the 6.7L Power Stroke has all but been perfected by Ford, and hundreds of thousands of happy customers agree. Its reputation for reliability and high-mile durability is often compared to the venerable 7.3L—although the 6.7L racks up its miles with significantly more power on tap, cleaner emissions, and vastly-improved drivability. Its performance potential and dependability has even converted Duramax and Cummins fans to Ford owners.

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So why is the 6.7L Power Stroke so great? After all of the issues associated with the 6.0L Power Stroke were followed by rampant emissions-related, fuel system, and hard-part failures on the 6.4L, the Dearborn automaker desperately needed a homerun engine for its Super Duty line. By taking its diesel engine program fully in-house and bringing outside experts onboard to help with its development, FoMoCo delivered. In the grand scheme of things, Ford’s 6.7L may have even saved the Power Stroke name. It might not be the greatest compression-ignition power plant ever created, but it is arguably the best Power Stroke ever assembled. In the following pages we’ll explain why.

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Big low-rpm torque, insurance to facilitate future increases in cylinder pressure (i.e. torque), substantial weight reduction and improved noise, vibration, and harshness (NVH) all pointed Ford in the direction of using compacted graphite iron (CGI) for the 6.7L’s block rather than conventional gray iron. Thanks to CGI’s superior strength (it can be as much as 75-percent stronger than gray iron), critical areas of the block that would normally require a lot of meat can be cast much thinner.

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Use of a CGI crankcase was one of many firsts the 6.7L Power Stroke brought to the ¾-ton and larger truck segment. All blocks are cast by Tupy, where they also receive their initial machining. From there, the blocks are shipped to Ford’s Chihuahua, Mexico engine plant. Notice the block’s deep-skirt design, which did away with the bed plate employed on both the 6.0L and 6.4L Power Strokes.

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The 6.7L Power Stroke might not employ a bed plate, but it does utilize cross-bolted main bearing caps with six bolts apiece. For utmost ductility, the main bearing caps are made from nodular iron. Not surprisingly, they secure a crankshaft that’s constructed of forged-steel. The crankshaft’s 4.25-inch stroke is the longest of any Power Stroke built to date.

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Another departure from the 6.0L and 6.4L, the 6.7L Power Stroke features six head bolts per cylinder (with sharing) as opposed to four. With an abundance of head fasteners helping to contain cylinder pressure, each bolt’s outer diameter measures 12mm (vs. 14mm on the 6.0L, and 16mm on the 6.4L).

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Locating the oil cooler on the outside of the left side of the oil pan has proven beneficial, along with being packageable. Remember, on both the 6.0L and 6.4L it was located at the front of the lifter valley within the block. On the 2011 6.7L, it mounts to the oil pan by bolts present on the outside of the pan and a nut on the inside of the pan, which seals the center port of the oil cooler. Starting with ’12 model year engines, the hidden internal mounting point was done away with so that the oil cooler could be removed without have to pull the lower oil pan.

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Further weight savings measures on the 6.7L included reducing the rotating mass of the engine. This reduction directly led to thinner connecting rods. But even though the fractured-cap, powdered-metal rods aren’t as beefy as the units employed in preceding engines, the aftermarket has proven they’re still capable of handling 700-rwhp. On the small end of each rod, you’ll find an offset wrist pin and an aluminum piston cast by Mahle with a single cooling galley. In engines produced before January 7, 2016, 34mm wrist pins were used. Since then, 35mm pins have been employed.

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Aluminum cylinder heads weren’t anything new to the truck segment when the 6.7L Power Stroke arrived (hint: Duramax), but the reverse-flow design was. Reverse flow means the exhaust manifolds are located in the valley (inboard side of the heads) rather than on the engine’s outboard side. By packaging the exhaust manifolds in this fashion, the turbocharger is made much more efficient thanks to reducing the loss of radiant heat.

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In addition to dissipating radiant heat much better than cast-iron heads, the 6.7L Power Stroke’s heads make use of 4 valves per cylinder. And contradictory to what most reverse-flow heads do (flow less than traditional, cross-flow style heads), in their forced induction application they move enough air to support 500 to 540-rwhp on a simple tune (500hp on ’11-’14 engines, 540hp on ’15-’19 engines). Aside from exhaust valve issues surfacing on ’11 model year engines (which in some cases led to them cracking and then causing catastrophic failure), the cylinder heads have proven solid since 2012.

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Due to the design of the reverse-flow heads, the valve covers and intake manifold are essentially one piece. Cold side air coming from the air-to-water intercooler flows through the upper intake plenum into the top of the valve cover. The intake manifold is incorporated into the valve cover internally, and on the underside (head side).

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On other aspect that makes the 6.7L Power Stroke very unique in the truck segment lies in its valvetrain. Each valve has its own rocker arm and pushrod. No more floating bridge used to open two valves. Despite the valvetrain’s complexity, it has proven highly reliable. Also advantageous is the fact that the rocker arms aren’t attached to the heads via the head bolts.

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Not only does each valve having its own rocker arm cut down on NVH, but a dedicated fulcrum for each individual rocker greatly reduces rocker arm pivot wear. If you recall, the 6.4L Power Stroke had major wear issues at the rocker arm fulcrum, and it’s obvious Ford made sure this was designed out of the equation on the 6.7L.

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To aid valvetrain longevity, a rocker arm oiling manifold is present within the top of each head. The dual purpose chamber serves as a means to lubricate and cool both the valves and the rocker arms.

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State-of-the-art a decade ago and still in use today, the Bosch CP4.2 high-pressure fuel pump was at the heart of the 6.7L Power Stroke’s common-rail system. The twin-piston pump brought 30,000-psi injection pressure to the table and the eight-hole piezo electric injectors downwind of it offered the quietest injection events Ford diesel owners had ever heard. Though the CP4.2 has developed a reputation for failing and taking out the injectors when it goes, most of those instances occur in LML Duramax applications, where no factory lift pump is present. Thanks to a factory lift pump supplying approximately 55-psi to the CP4.2, CP4.2 failure is much less common on the 6.7L Power Stroke.

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Blazing a new trail in charge air cooling, Ford bucked convention and included an air-to-water intercooler on the 6.7L Power Stroke—yet another first for the pickup truck market. Chosen for its unmatched efficiency and ease of packaging, the air-to-water intercooler is tied in with the engine’s secondary cooling system, which also serves the transmission, EGR, and fuel cooler.

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Nearly from day one, the dual compressor wheel, ball bearing Garrett GT32 SST variable geometry turbo found on all ‘11-’14 engines proved problematic. It seemed that any additional power beyond stock could overspeed the tiny VGT, so the aftermarket stepped in with a sound solution. Companies like H&S Motorsports, Midwest Diesel & Auto, Maryland Performance Diesel and RCD Performance offer T4 mounting kits to accommodate a fixed geometry charger, usually an S300 frame BorgWarner (shown). In the process of switching to a more reliable turbo, bolting a 63mm to 66mm version of the S300 to the 6.7L Power Stroke often yields gains of 70 to 100hp, which serves as further proof of just how restrictive the factory GT32 SST is.

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After the ’15 model year engine debuted with the more conventional, single compressor wheel VGT, the Garrett GT37, the job of converting older engines to the new style charger using OEM components became commonplace. Once again, in making the switch to a higher flowing turbo, significant gains can be had. And if the customer wants to open things up beyond what the OEM 61mm GT37 offers, various drop-in 63mm to 66mm upgrades exist.

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If you’re looking to making solid power on a stock bottom end, this is the way to go: a big single in the valley. For trucks running dual pumps or a stroker CP4.2 and stock or a mild nozzle upgrade, you can knock on the door of 700-rwhp without building the kind of rod-bending torque a VGT or a set of compounds produces. Snyder Performance Engineering, Maryland Performance Diesel, and BD Diesel offer pedestals or complete single turbo kits to make running an S400 on your 6.7L Ford a reality.

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The 6.7L Power Stroke’s performance potential even attracted the attention of Fleece Performance Engineering, a company known for its drop-in “Cheetah” turbo options for the Duramax and Cummins camps. After developing a killer 63mm direct replacement VGT that spools like stock and supports 650-rwhp they can’t build them fast enough. After all, with a second high-pressure fuel pump or a single stroker pump, 650hp is already at your fingertips with the 6.7L, so the cost to play is anything but outrageous.

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Even with weaker rods than what the 6.4L had, tuners and enthusiasts have found a way to make stock rods live at 700-rwhp. For those looking for more than that, RCD Performance, Wagler Competition Products and Carrillo manufacture stronger rods, which have all been proven to handle more than 1,200 hp. Perhaps most popular, Carrillo’s H-beam rod (called its Pro-H design) is made of forged-steel, and comes standard with H-11 tool steel 7/16-inch rod bolts.

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Thus far, the factory cast-aluminum pistons haven’t been much of a weak link. Starting with OEM Mahle units sized from standard bore all the way up to 0.040-inch over, many receive de-lipped fuel bowls, ceramic coating, and fully radiused valve reliefs during a full-on 6.7l build. Upgraded, H-13 tool steel wrist pins that won’t flex under big torque load are also available from RCD Performance, along with a gapless second ring option.

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Slipping the crank gear can spell disaster for the 6.7L Power Stroke, and unfortunately it’s somewhat common on higher horsepower, stock bottom end engines. The age-old trick of TIG-welding the crank gear to the crankshaft rules this out, and tacking the cam gear permanently in place is also a good idea while you’re in there. This can be done with the engine in the truck and the transmission still in place, although reinstalling the front cover can be a chore, to say the least.

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Oil pressure can be very inconsistent on the 6.7L Power Stroke, with only 38-40 psi observed when some engines see high load. H&S Motorsports’ billet oil pump regulator solves this problem and has become an automatic upgrade for many 6.7L engine builders. The H&S regulator provides for 60-80 psi (depending on your engine’s specific bearing tolerances) under high load conditions.

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Though thousands of 6.7L owners have been getting away with making 650hp or more on bone-stock valvetrains, valve creep and valve float are still major concerns with elevated boost, drive pressure, and rpm in the mix. Once you’re forced to break the seal on the 6.7L Power Stroke (whatever the reason), it behooves you to install chromoly pushrods and stiffer valve springs at a minimum. The upgraded springs shown here from RCD Performance carry a 110-lb seat pressure, which is ideal for engines with larger VGT’s, big fixed geometry singles, or compounds.

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When horsepower, torque, boost, and drive pressure all go up, so does the chance of popping a head gasket, and ARP wasted no time developing head studs for the 6.7L Power Stroke. Its ARP 2000 material studs are rated for 200,000 psi tensile strength and should be torqued (in three sequences) to 125 ft-lbs. For precise main cap alignment and the resulting optimum bottom end strength, ARP also offers main studs as well.

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Much more potent than the solenoid valve style injectors found in ’01-’10 Duramax and ’03-‘18 Cummins applications, minimal nozzle size increases on the Bosch piezo units used on the 6.7L Power Stroke can support huge horsepower. For example, 60-percent over nozzles can make in excess of 850hp possible when matched with proper airflow. Exergy Performance and S&S Diesel Motorsport are the utmost authorities on high-flow, fully-balanced piezo injectors in the aftermarket.

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While adding a belt-driven CP3 on top of the stock CP4.2 was common practice for supporting injector upgrades in the early years of the 6.7L Power Stroke, stroker pumps have been all the rage as of late. The 10mm CP4.2 produced by Exergy Performance flows 30-percent more fuel than a stock ’15-’19 pump and is rated to support 800hp, but many believe 900hp is possible (again with adequate airflow). In conjunction with a compound turbo arrangement where Fleece’s 63mm VGT Cheetah and a Precision 76mm atmosphere charger were being employed, Exergy’s stroker CP4.2 allowed one 6.7L Power Stroke owner to clear 730-rwhp on stock injectors.

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High quality, above-average fitment, and huge horsepower potential highlight the compound systems offered by No Limit Fabrication. Its add a turbo kit comes standard with a ball bearing, 76mm atmosphere charger from Precision Turbo & Engine, with 82mm, 83mm, and 86mm versions also available. If you want to make 800hp or more and still tow anything you need to, this is the system for you. Just don’t forget to build the bottom end first.

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As we went to press, H&S Motorsport had just released its triple-turbo kit for the 6.7L Power Stroke. The two-stage, triple system comes with a sizeable price tag, but as with anything H&S makes, it features a comprehensive parts list and the highest quality components you’ll find anywhere in the diesel industry. Based around the use of its single T4 turbo mount, you can opt to run either a BorgWarner S300 SX-E or billet wheel S400 in the valley, while two BorgWarner S300’s (sized between 63mm and 72mm) essentially act as a single atmosphere charger on the passenger side of the engine.