A Low-Key Cummins, Built To Yank The Sled The Furthest

When we heard there was an engine making more horsepower than anything else on the local Work Stock pulling scene, we had to see it for ourselves. Our curiosity brought us to LinCo Diesel Performance, where a trip to the engine dyno at S&S Diesel Motorsport yielded some big numbers. All told, the LDP-built 6.7L Cummins made 54 pulls—52 of which were over 1,000 hp. Peak power checked in at 1,110 hp at the crank, which is pretty impressive when you consider the engine has to breath through a factory-based turbo. Trust us, the fact that a stock-appearing HE351CW Holset and the factory intake shelf support north of 1,100 make this Cummins an absolute sleeper in the world of truck pulling.

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All machine work took place at LDP machine in Troy, Missouri, and the team there got started by decking the 6.7L Cummins block. Standard deck height was the target here, just to clean up the core block’s surface.

So what’s the engine’s secret? Without giving too much away, LinCo gave us the tour from top to bottom. From machining the block, re-working the head, and lightening the crank to deciding on the right camshaft, injector, and CP3 options, some of the best parts and pieces in the diesel world were chosen for the build. Names like Hamilton, XDP, ARP, Bean Machine, Wagler, S&S, Tater Built, and Pusher Intakes all had a hand in the effort, and although we aren’t giving the owner’s name away (or the truck’s), by now he’s likely the one nobody else can beat on the Missouri/Illinois Work Stock circuit…

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A lightened, factory-based 6.7L Cummins crankshaft was sourced from Hamilton Cams and underwent balancing at LDP Machine. Notice the lack of counterweights? By removing the counterweights, the crank’s overall weight was reduced by 31 pounds.
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A lightened, factory-based 6.7L Cummins crankshaft was sourced from Hamilton Cams and underwent balancing at LDP Machine. Notice the lack of counterweights? By removing the counterweights, the crank’s overall weight was reduced by 31 pounds.
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To tie the main caps together and reinforce the block, a gridlock girdle from Bean Machine got the call. Made of aluminum, Bean’s girdle doesn’t add unnecessary weight in accomplishing its goal of adding rigidity, and it also incorporates dowels that lock the mains in place. The complete gridlock girdle kit came with 12mm diameter ARP main studs.
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Opting for a 6.7L Street Performance cylinder head from Hamilton Cams was a great starting point—a head with 1.5-inch diameter intake and exhaust valves and that flows 226 cfm per cylinder—but then LDP Machine made things even better. To aid cfm flow at low cam lift (on both the intake and exhaust), the valves were un-shrouded. Additionally, LDP chamfered, beveled, and smoothed out the valve throats, finishing them by hand.
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Once the valve un-shrouding work had been performed, the head was cut to accept fire-rings. We’ll note that both the block and head were fire-ringed for this build, whereby the fire-ring sits in both the block and head to form the best combustion seal possible.
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Wagler Competition Products supplied a set of Street Fighter connecting rods for the build. Forged from 4340 and then shot-peened to reduce stress risers, they’re rated for up to 1,500 hp. The rods came with ½-inch ARP L19 rod bolts and were fitted with Clevite H-series rod bearings, which will see CenPeCo 20W-50 high performance racing oil throughout the duration of their lifespan.
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The Street Fighter rods utilize Wagler’s state-of-the-art, dual angled tongue-and-groove design, which aligns and locks the cap in place to eliminate offset caps and maintain a true bore. Peering into the bottom of the block, you can see one of the ½-inch ARP L19 rod bolts that secure each rod cap.
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LinCo obtained the engine’s cast-aluminum pistons through Interstate-McBee. They started out as 6.7L QSB replacement pistons, but were fly-cut 0.050-inch deep for the intake valves due to LinCo advancing cam timing 2 degrees—a bump that moves the power curve lower in the rpm range (for more airflow in this air-limited application). The pistons were also fitted with Total Seal gapless second rings for better oil control and lower oil consumption.
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Before assembly, the QSB pistons were treated to a high-temp thermal barrier up top to stand up to the 1,600-1,750-degree F EGT they would see. Teflon coating was applied to the piston skirts to reduce friction, while the wrist pins were DLC coated for the same reason. Contrary to popular belief, LinCo did not build a “loose” engine. Piston-to-wall clearance is on the tight side, at 0.005-inch. In the photo shown here, the Hamilton-supplied standard thickness fire-ring head gasket is in place on the block.
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Here you can see the process of degree-ing the camshaft to ensure the intake and exhaust valves open at the proper interval. One of Hamilton’s steel 188/220 cams is being employed—a cam with a 1,700 to 4,500 rpm operating range—along with the company’s 1.45-inch, DLC coated steel tappets.
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A 6.7L Fluidampr sits on the end of the crankshaft, complete with heat-treated, high strength, and extended length ARP retention bolts. Fluidampr’s full power kit is also in use, where a ½-inch thick torque plate (with textured finish) mounts between the damper face and bolts, and provides a wider and stronger clamping surface.
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At the top of the valvetrain, the factory rocker arm bridges were ditched in favor of Xtreme Diesel Performance’s billet replacements. Not only are the 4140 chromoly units much stronger than factory, but they feature oiling holes for the valve stems.
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Good to 6,500 rpm, Hamilton Cams’ 110-pound valve springs provide the type of high-rpm insurance every high-dollar, competition engine needs. They provide 110 pounds of seat pressure and should not be confused with the company’s popular 103-lb springs. These aren’t for the street.
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Twelve of Hamilton Cams’ extreme duty pushrods complete the engine’s valvetrain operation. Made from heat-treated chromoly and of a three-piece design, each 12mm diameter pushrod features a 0.120-inch wall thickness. The rocker arms came from Hamilton, too, and feature DLC coated trunnions.
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The job of clamping the worked-over cylinder head to the block was given to ARP’s 12mm Custom Age 625+ head studs. For an application that sees less than 60-psi of boost (but more than 90-psi of drive pressure), they’re the kind of overkill that will keep this engine problem-free no matter what kind of abuse it sees. Also notice the thread-in style freeze plugs in the head, a common process to eliminate the factory pressed-in plugs from blowing out under high heat and/or pressure.
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For any high rpm Cummins, the factory freeze plugs in the block are prone to failure. To rule that out, one of Keating Machine’s billet freeze plug kits was installed. The rear plug, front plug, and three side freeze plugs were all replaced with bolt-in versions that won’t blow out under high engine speed or excessive pressure.
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One more remedy for excessive coolant pressure checks in in the form of an electric water pump. The factory Cummins water pump is known to produce immense pressure at high rpm. This unit, which flows 50-gpm, will keep coolant circulation pressure consistent throughout the engine’s rpm range.
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Following the new engine’s 54-pull beat-down on the dyno, LinCo tore into the Cummins to inspect the bearings. They were pleased (as were we) to find dial indicator marks still present on the rod bearings.
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A 14mm CP3, also from S&S Diesel Motorsport, keeps a factory 6.7L fuel rail topped off for the injectors to use. The pump boasts a stroker shaft (hence the 14mm designation), redesigned buckets, has been optimized for high speed, and can support roughly 1,400 hp.
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Custom-built at S&S Diesel Motorsport for this specific, air-limited application, the engine’s injectors underwent extensive internal body modifications prior to being fitted with 350-percent over nozzles. For additional flow, S&S also removed the internal diffuser in each fuel crossover tube.
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For improved engine tunability, a 2400 bar (34,800 psi) fuel rail pressure sensor from S&S is employed. One of S&S’s 2400 bar pressure relief valves is used as well to help vent excess rail pressure.
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An angled, 24-valve version of Steed Speed’s second-gen T4 divided exhaust manifold helps drive the turbo as efficiently as possible. Like all Steed Speed manifolds, it’s made from mild steel, but features the company’s satin black Techline coating. The high-temp coating is rated for 1700 degrees F continuous, and can handle short periods of 2,000 degrees.
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To accommodate the T3 foot, stock-appearing turbo, LinCo turned to Stainless Diesel for one of its T4 to T3 adapters. With a 1-inch thick steel spacer, a T3 gasket, T4 gasket, and all mounting hardware, Stainless’s complete adapter plate kit made accommodating the HE351CW charger as straightforward as possible.
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If anyone knows stock-appearing turbos, it’s Tater Built Turbochargers. They’ve been at the top of the game a while now, and this version of the HE351CW moves way more air than you think. Machined to accept a 7-blade compressor wheel with a 71mm inducer and a proprietary, 10-blade turbine wheel with a 71mm exducer, the 71/71 (as we heard it referred to) produced 58 psi of boost. It still sports a factory 9cm exhaust housing but does come with an upgraded wastegate, which made a noticeable difference when adjusted on the dyno (and namely the aforementioned 58-psi boost number).
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Pusher Intakes’ Mega intake elbow, with dual 3.5-inch mandrel bent tubes joined together, feeds air through a G&R Diesel billet grid heater delete, and ultimately into the head. If making 1,100 hp on the factory intake shelf surprises you, it’s rumored that as much as 1,500 hp can be squeezed through it before the process of milling it off and adding an aftermarket intake manifold becomes a necessary.
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In the world of truck pulling, dyno sessions serve as an opportune time to try out multiple turbo options, which is exactly what the folks at LinCo did while visiting S&S Diesel Motorsport’s engine dyno. However, after making 1,078 hp on the first day of testing, it was clear that the Tater Built 71/71 was the best candidate. On Day two, 1,099 hp was made prior to the team noticing they’d lost a turbo gasket. Then, following a call to Tater Built Turbochargers the wastegate was adjusted and the engine responded by making 1,102 hp, 1,108 hp, and finally 1,110 hp.
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Working closely with Hamilton Cams on head flow and camshaft design, both parties definitely got it right with this engine. Not only does the 6.7L Cummins turn out 1,110 hp at its peak, it makes 1,050 hp or more from 3,000 rpm through 4,200 rpm. These numbers are on par with what Pro Street pulling engines are making—the smooth bore 2.6 trucks you see at the Scheid Diesel Extravaganza and along the Pro Pulling League’s Western Series circuit.

SOURCES

ARP
800.826.3045
arp-bolts.com

Bean’s Diesel Performance
844.237.7467
beansdieselperformance.com

Fluidampr
716.592.1000
fluidampr.com

G&R Diesel
330.695.2039
grdiesel.com

Hamilton Cams
512.355.9101
hamiltoncams.com

Interstate Mcbee
216.881.0015
interstate-mcbee.com

Keating Machine
865.599.6499
keatingmachine.com

Linco Diesel Performance
636.528.1577
lincodieselperformance.com

Mahle
mahle-aftermarket.com

Pusher Intakes
772.589.8385
pusherintakes.com

S&S
ssdiesel.com

Stainless Diesel
574.358.0456
stainlessdiesel.com

Steed Speed
250.807.7212
steedspeed.com

Tater Built Turbochargers
567.208.2227

Wagler Competition Products
812.636.0391
waglercompetition.com

Xtreme Diesel Performance
888.343.7354
xtremediesel.com

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