The 6.7L Cummins had much to prove when it first appeared on the scene for the ‘07.5 model year Dodge Rams. After all, the 5.9L engine that succeeded it was renowned for its million-mile endurance, massive performance potential, and seemingly limitless aftermarket parts and maintenance. Fortunately, more than 40% of the Cummins 6.7 performance engine internals were carried over from the 5.9L engine, and its injection system was kept practically unchanged.

The 5.9L Cummins common-rail engine was produced from 2003 to 2007 and had a fixed geometry turbo. By the end of its run, it produced 325 horsepower, 610 lb-ft of torque, and 359 ci of capacity from a stroke of 4.72 in and a bore of 4.02 in. The 6.7L Cummins engine debuted in 2007.5 generation year Ram pickups, producing 350 horsepower and 650 lb-ft of power. It had a variable geometry turbo, a bore of 4.21 in, a stroke of 4.88 in, and a displacement of 408.2 ci.

However, the 6.7L would be burdened with the full suite in terms of emissions control devices – something 5.9L owners were completely unaware of. The new 6.7L Cummins engine included EGR and a DPF. In the 2013 model year Rams, SCR would be introduced to the mix, requiring diesel exhaust fluid as a component of the exhaust post-treatment method to lower NOx emissions.

The trade-offs have begun! Because of the abovementioned emission reduction components, fuel efficiency and general reliability are notably poorer on 6.7L-equipped trucks. However, the 6.7L’s dynamic geometry turbocharger makes it more reactive at low rpm than the 5.9L, not to mention that it has a highly efficient exhaust brake function. The 6.7L’s greater displacement also contributes to significantly more power, perfect for truck owners who spend a lot of time tied up to a trailer.

While many people still feel the old 5.9L is the be-all and end-all Cummins, many others have accepted that the 6.7L is a better upgrade to the 5.9. And this is why:

Similar injectors

While the injectors used in the 5.9L and Cummins 6.7 performance engine appear to be the same size, the 6.7L version is built and qualified for greater pressure (and also needs lower voltage to work them). Unlike the 5.9L injectors, the 6.7L injectors are programmed to the ECM of each unique truck, and injectors cannot be switched into other cylinders.

The function of the exhaust brake

The exhaust brake, to be precise. Essentially a turbo brake, the HE351VE’s dynamic geometry design could be used to generate significant braking power, reducing wear on the truck’s service brakes. The 8,000-pound mass of a ‘07.5-present Ram may be slowed very quickly by adjusting the location of the nozzles to produce greater restriction. The Holset HE351VE is unrivaled in its capacity to slow a vehicle among all newer models of trucks (even ’11-present Fords and ’11-present GMs) in the exhaust brake arena. To cut a long story short, the HE351VE’s effective and aggressive exhaust brake function transforms 6.7L Rams into towing machines.

Strong foundation

After over a decade of production, the 6.7L block has become the favored foundation in diesel motorsports, owing to its Siamese cylinder bore configuration and displacement advantage. Several businesses in the upper echelons of the truck pulling and drag racing add a deck plate on top (to prevent the tops of the bores from warping) and sleeves to the cylinders and lengthen the crank stroke. 6.7L blocks subjected to this machining style typically have 390 cubic inches of displacement, produce around 1,800 and 3,000 horsepower, and do it in an extremely reliable manner.

The Cummins 6.7 performance engine has been modified to increase responsiveness and road handling. It has remarkable torque ratings for exceptional towing performance while remaining fuel-efficient.