Family Lineage – The Evolution Of The Dodge/Ram Diesel Engine


No matter which brand you are loyal to, looking back at the company history, and more importantly the engine history, can be a deciding factor in future purchases. Knowing where your favorite brand’s engines came from can help give you a sense for where they might be going, and if purchasing an older engine, what you can expect to experience.

12 Valve Engine Specs

  • Bore: 4.02 inches
  • Stroke: 4.72 inches
  • Displacement: 359 cubic inches (5.9-liter)
  • Injector:  Direct Injection
  • Pump: VE Rotary Pump (1989-1993); inline injection pump (P-Pump) (1994-1998)
  • Turbo: Single Holset
  • Base Horsepower and Torque
  • 1989-1993:
    • 160 hp at 2,500 RPM
    •  400 lb-ft at 1,600 RPM
  • 1994-1995:
    • 160 hp at 2,500 RPM (auto)
    • 400 lb-ft at 1,600 RPM (auto)
    • 175 hp at 2,500 RPM (manual)
    • 420 lb-ft at 1,600 RPM (manual)
  • 1996-1998:
    • 180 hp at 2,500 RPM auto/CARB
    • 420 lb-ft at 1,600 RPM auto/CARB
    • 215 hp at 2,600 RPM (manual)
    • 440 lb-ft at 1,600 RPM (manual)
  • Emissions: Catalytic Converter, CARB trucks EGR
1989 – 1998

Ah, the beloved 12 valve. The first year Dodge offered a 5.9-liter Cummins engine was 1989. These inline six-cylinder engines were direct injected and turbocharged. Everything about this engine was drastically different than the competition. The Cummins was the only inline six-cylinder offered (still is), the only direct injected and turbocharged engine of “the big three.” The 5.9-liter featured two valves per cylinder (i.e. 12 valve) and utilized solid lifters. Between 1989 and 1993, the engine had a Bosch VE44 rotary injection pump. In 1994, the rotary pump was ditched for the infamous inline injection pump, the P7100 P-Pump.

A Holset turbocharger has always been used, and the initial production years didn’t use an intercooler. In late 1991, that changed as an intercooler became standard from that point on. Even with the addition of an intercooler, no horsepower and torque increase was made until 1994 when the P7100 P-Pump was added. Also, 1994 marked the addition of a catalytic converter, and in 1996 the California Air Research Board (CARB) emissions certified trucks received an Exhaust Gas Recirculation (EGR) valve.

The presence of the P7100 injection pump marks the split horsepower ratings between manual and automatic transmissions.


The 12 valve engines are the easiest to spot due to the individual valve covers. This one belongs to Doug Brarens and resides in his 1939 Chevy Rat Rod.

24 Valve Engine Specs

  • Bore: 4.02 inches
  • Stroke: 4.72 inches
  • Displacement: 359 cubic inches (5.9-liter)
  • Injector:  Direct Injection
  • Pump: VP44 Rotary Pump
  • Turbo: Single Holset
  • Base Horsepower and Torque
  • 1998-2000:
    • 215 hp at 2,700 RPM (auto)
    • 420 lb-ft at 1,600 RPM (auto)
    • 235 hp at 2,700 RPM (manual)
    • 460 lb-ft at 1,600 RPM (manual)
  • 2001-2002:
    • 235 hp at 2,700 RPM (auto/manual)
    • 460 lb-ft at 1,600 RPM (auto/manual)
    • 245 hp at 2,700 RPM (High Output)
    • 505 lb-ft at 1,600 RPM (High Output)
  • Emissions: Catalytic Converter, CARB trucks EGR
1998 – 2002

Cummins entered the computer age (well kind of) with the 24 valve. This next generation of Cummins to hit the market in 1998 brought quite a few changes with it. The two biggest changes were the addition of the VP44 electronically controlled rotary injection pump and the four-valve-per-cylinder head. While the injection pump was still primarily mechanical, the regulation of the pump was done electronically. Cummins refered to this new engine as an ISB (Interact System B-series), but enthusiasts have always called it the 24 valve.

While most of the engine was actually redesigned, its basic configuration remained the same. There are some issues with this generation of engines. As with Ford and its head gasket problem in the 6.0’s, the 1998 to 2001 24 valves have block-cracking problems. This has been traced to faulty castings at one of the plants. All of the affected blocks have a number 53 embossed on them.


The 24 valve engines did not come with factory compounds. This engine resides in Brandon Carr’s 1972 Buick Riviera.

Common Rail Engine Specs

  • Bore: 4.02 inches
  • Stroke: 4.72 inches
  • Displacement: 359 cubic inches (5.9-liter)
  • Injector: Direct Injection
  • Pump: Bosch CP3
  • Turbo: Single Holset
  • Base Horsepower and Torque
  • 2003-2004:
    • 235 hp at 2,700 RPM (CARB)
    • 460 lb-ft at 1,400 RPM (Except H.O.)
    • 250 hp at 2,900 RPM (Non-CARB)
    • 460 lb-ft at 1,400 RPM (Except H.O)
    • 305 hp at 2,900 RPM (High Output)
    • 555 lb-ft at 1,400 RPM (High Output)
  • 2004.5:
    • 325 hp at 2,900 RPM (all)
    • 600 lb-ft at 1,600 RPM (all)
  • 2005-2007:
    • 325 hp at 2,900 RPM (all)
    • 610 lb-ft at 1,600 RPM (all)
  • Emissions: Catalytic Converter and EGR varies by year.

The third revision of the 5.9-liter Cummins brought about a whole new standard in idle sound quality. The 24 valve engines are arguably the noisiest, and the new common rail engines are arguably the quietest (when they entered the market in 2003). The most notable improvement came from a new fuel system. The VP44 rotary injection pump was replaced with a Bosch CP3 high-pressure fuel pump feeding a single common high pressure fuel rail. All of the injectors were connected to this fuel rail and saw the same high pressure. The injectors were now electronically controlled, allowing for multiple injection events during each combustion cycle. By using multiple injection events, the noise could be better controlled and regulated (it also helped with emissions).

From a structural standpoint, the engine block was strengthened and a bed plate was added. Most of the rotating assembly remained unchanged. The front timing cover and gear drives were changed to fit the CP3 fuel pump.


6.7 Engine Specs

  • Bore: 4.21 inches
  • Stroke: 4.88 inches
  • Displacement: 408 cubic inches (6.7-liter)
  • Injector: Direct Injection
  • Pump: CP3 Bosch high pressure fuel pump
  • Turbo: VGT turbo
  • Base Horsepower and Torque
  •  2007-2010:
    • 350 hp at 3,000 RPM (all)
    • 650 lb-ft at 1,500 RPM (auto)
    • 610 lb-ft at 1,500 RPM (manual)
  •  2011-2012:
    • 350 hp at 3,000 RPM (all)
    • 800 lb-ft at 1,600 RPM (auto)
    • 610 lb-ft at 1,500 RPM (manual)
  • 2013- present:
    • 350 hp at 2,800 RPM (manual)
    • 660 lb-ft at 1,500 RPM (manual)
    • 370 hp and 2,800 rpm (68RFE auto)
    • 800 lb-ft at 1,700 RPM (68RFE auto)
    • 385 hp at 2,800 RPM (Aisin AS69RC auto)
    • 850 lb-ft at 1,700 RPM (Aisin AS69RC auto)
  • Emissions: Catalytic Converter, EGR and DPF.

This marks the first real major redesign of the 5.9-liter Cummins since its introduction in 1989 in the Dodge Rams. The new 6.7-liter engine remained an inline six-cylinder with a bore of 4.21 (up from 4.02) inches and a new longer stroke of 4.88 (up from 4.72) inches. Feeding all of that additional displacement is a Variable Geometry Turbocharger (VGT) which helps create boost down low by changing the internal vanes to increase the pressure of the exhaust gasses contacting the turbine blade.  On the big end, the vanes open up helping to reduce back-pressure to support top-end horsepower. The engine meets 2010 emissions, which means that the engine features an Exhaust Gas Recirculation (EGR) cooler, Diesel Particulate Filter (DPF), and catalytic converter.

A huge effort was spent quieting the engine down and the 6.7-liter is actually 50 percent quieter than the previous generation 5.9-liter. In addition, for the first time, a factory exhaust brake is optional.

2014 Ram Heavy Duty

About the author

Chad Westfall

With diesel running through his veins from childhood, Chad has more than a decade of experience in the automotive industry. From editorial work to wrenching, there isn’t much he hasn't conquered head-on. When he’s not writing and shooting trucks and tech, you’ll find him in the shop working on turning the ideas floating around in his head into reality.
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