Cutting-Edge Sled Puller Cummins

A Third-Gen Sled Puller Squeezing More Than 1,100HP Out Of A Stock Appearing Turbo

When a broken crankshaft took John Koppelmann’s daily-driven ’07.5 Dodge off the road—the truck he’d originally bought when he turned 21—he knew it would be down a while. Then the wheels started turning and John decided it was time to get back into a sport he’d been away from for roughly eight years: truck pulling. But instead of pulling the 6.7L Cummins for a simple rebuild and mild upgrades, John set his sights on building a fire-breather of an engine to stir things up in the local, highly-competitive Work Stock class. What soon unfolded was a Cummins build like no other—one where 1,110 hp would somehow be forced through a stock-appearing turbocharger.

Overbuilt During The Overhaul

John’s search for a quality machine shop brought him to LDP Machine in Troy, Missouri, where the 6.7L was promptly disassembled, the block decked, and the mains treated to a line-hone. A lightened OEM-based crankshaft from Hamilton Cams is tied in with the main caps by way of a Bean Machine gridlock girdle with ARP main studs, while the rest of the rotating assembly consists of Wagler Street Fighter rods and valve-relieved (and coated) QSB pistons. And with the Cummins destined to live at high rpm, a 188/220 Hamilton cam that’s good for 4,500 rpm was chosen to actuate the valvetrain.

Unrestricted Cylinder Head

Starting with a ported head from Hamilton Cams, LDP took it a step further by un-shrouding the valves and chamfering, beveling, and smoothing out the valve throats for improved cfm flow at low cam lift. The worked over 24-valve piece also benefits from Hamilton’s 110-lb valve springs, Xtreme Diesel Performance’s billet rocker arm bridges, thread-in style freeze plugs, and we’ll note that both the head and block were machined to accept fire-rings. ARP Custom Age 625+ 12mm head studs keep the head fastened to the block. One other aspect of the engine build that’s worth mentioning is that the factory intake shelf remains. John’s build, and subsequent dyno tested, proves there is no need to send your head through the mill to remove it for a goal of 1,100 to 1,300 hp.

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Built from the ground-up at LDP Machine, John Koppelmann’s 6.7L Cummins sports a balanced and lightened 6.7L crankshaft, which is anchored in place via a Bean Machine gridlock girdle and 12mm ARP main studs. The factory 6.7L-based crank swings a set of Street Fighter rods from Wagler Compeition Products, which are topped off with fly-cut and coated 6.7L QSB pistons. Hamilton’s 188/220 camshaft was chosen for its high-rpm efficiency (4,500 rpm), along with the company’s coated steel tappets. Out in front of the intercooler, four 12-inch diameter electric fans force air across the factory radiator.

The Little Turbo That Could

Because Work Stock class rules allow unlimited sizing for competitors who choose to run a stock-appearing turbocharger, John teamed up with Tater Built Turbochargers to get the most out of the Holset HE351CW. Its 71mm compressor wheel forces plenty of air into the engine, and a 71mm turbine wheel offers great flow on the exhaust side. During the course of a pull, John reports as much as 55-psi of boost being created by the Holset. The Tater Built 71/71 hangs from a T4 second-gen 24-valve style Steed Speed exhaust manifold thanks to a Stainless Diesel T4 to T3 adapter.

Holding down the fort, you’ll find ARP Custom Age 625+ 12mm head studs. The 6.7L cylinder head itself is a fire-ringed, Street Performance unit from Hamilton Cams, which underwent valve un-shrouding and valve throats that were chamfered, beveled and smoothed by hand at LDP Machine. Other highlights include Hamilton 110-lb valve springs and XDP billet rocker arm bridges with oiling passages for the valve stems.

350-Percent Over Injectors & 14mm CP3 Turning S&S Diesel Motorsport loose on the fuel system, John received injectors with extensive internal body modifications and that are topped off with 350-percent over nozzles—along with a 14mm CP3. To support higher rail pressure, an S&S 2400 bar (34,800 psi) rail pressure sensor and a 2400 bar pressure relief valve are also in the mix. The stroker pump receives its low-pressure fuel supply from a 250-gph FASS system mounted on the driver side frame rail. Maverick Diesel ties every modification together using EFI Live in conjunction with the factory ECM.

G56 & Triple-Disc Clutch

John knew the 68RFE the truck originally came with would never hold up in the dirt, so the decision was easy to convert to a manual transmission. What might be surprising to some is the fact that he didn’t go with an NV5600 or even an NV4500. Instead, John’s Ram boasts a G56 gearbox, and it’s one that’s been beefed and rated for four-digit horsepower by SuperStick Transmissions. The six-speed is graced with a weighted, triple-disc competition clutch from Valair, and John leaves it in direct drive with the sled in tow.

A competition fuel system supplied by S&S Diesel Motorsport helps explain why more than 1,100 hp is produced at the crank. One of the company’s 14mm CP3’s sits in the factory location and the stroker pump feeds pressurized diesel to a set of custom-tailored injectors, which were treated to extensive internal body mods and 350-percent over nozzles. S&S’s 2400 bar (34,800 psi) fuel rail pressure sensor and a 2400 bar pressure relief valve are part of the system also.

With the option to run either a T4 S300 no larger than 66mm or a stock-appearing turbo in the Work Stock class, John chose the latter. Hiding a billet, 7-blade, 71mm compressor wheel, his Tater Built HE351CW means business. On the exhaust side, a 10-blade turbine with a 71mm exducer lives inside a factory 9cm2 housing. The high-flow Holset hangs from a 24-valve second-gen, T4 divided Steed Speed exhaust manifold courtesy of a Stainless Diesel T4 to T3 adapter. It builds 52-to-55 psi of boost going down the track.

After blowing a few intercooler boots on the engine dyno (where incredibly, the Cummins cleared more than 1,100 hp), several of BD Diesel’s boot lock kits were installed, along with 5-ply intercooler boots from Stainless Diesel. With boost now contained, it’s sent through an On 3 Performance intercooler and a Mega intake elbow from Pusher Intakes before entering the head via the factory intake shelf that’s still present.

GM And Power Wagon Parts

Surprisingly, not a lot has been done to the AAM axles underneath John’s third-gen. However, what is surprising is the fact that the rear AAM 1150, truss, and the corresponding leaf springs were originally found on an ’02 Silverado 2500 HD. It’s been fitted with a spool and a 4.56 ring and pinion, while the front AAM 925 is bone-stock other than the addition of an E-locker from a late-model Power Wagon. Adjustable suspension stops, traction bars, and a hitch from LinCo Diesel Performance all help ensure the truck is successful each time it hooks to the sled.

To keep the 14mm CP3 happy, a 250-gph Titanium Signature Series lift pump system from FASS is employed. Mounted along the driver side frame rail and pulling fuel from a sump in the bottom of the factory tank, the FASS lift pump sends a steady 16 to 18-psi worth of fuel pressure through ½-inch line at all times.

Nothing Is Off The Table

In 2021, the truck’s first year on the regional Missouri/Illinois Work Stock pulling circuit, John racked up approximately 15 wins behind the wheel of his Dodge. Given the fact that many competitive trucks in this category are dual-rear-wheeled and making close to or more than four-digit horsepower, that’s a pretty impressive accomplishment. John’s combination of big horsepower, a fine-tuned chassis, a reliable drivetrain, and aggressive tires make it possible. In the future, look for John to potentially branch out into the 2.6 smooth bore (Pro Street) class, try a dual rear wheel arrangement in Work Stock, and also step up to a newly-allowed 72mm S300. Never one to be deterred by travel, John and his cutting-edge Cummins might just come to dominate both pulling classes in 2022.