So, you’ve finally had enough of the troublesome Power Stroke engine that Ford stuffed between the frame rails of its otherwise sublime Super Duty pickup. Or you’re one of the few people who hates his or her big-block 8.1-liter gas-powered Chevy Silverado but otherwise loves the truck. If this sounds familiar, then it’s likely you’re one of the multitude of people who have considered undertaking a Cummins engine swap.

However, with so many different Cummins diesel engines produced throughout the decades, how is it ever possible to choose the right engine? In an attempt to bring clarity to the subject, we sat down with the experts at Diesel Conversion Specialists to help break down some of the key differences between the various generations of 5.9-liter and 6.7-liter Cummins inline six-cylinder engines used in Dodge and RAM Heavy Duty pickups.

These engines were produced from 1989 until now, and there have been more than three million put into service. The engines range in output from 160 to 430 horsepower and from 400 to 1,075 pound-foot of torque. The difficulty of installing one of these engines in a Ford or GM chassis ranges from simply adding 12-volt power and ground to basically needing an electrical engineering degree. In addition to the engine, you’ll also need to source proper engine mounts, a transmission or adapter, the necessary electronic controllers, intake and exhaust piping, along with everything to properly cool both the engine and intake air charge.

1989 – 1998: 12-Valve 5.9-liter Cummins

In the early years of the Dodge/Cummins partnership, Dodge fit its trucks with what is commonly referred to as a “12-valve” 5.9-liter Cummins inline six-cylinder turbodiesel engine. The “12-valve” refers specifically to the number of intake and exhaust valves fit to the engine, which in this case was two valves per cylinder (one intake and one exhaust) for a total of 12. What makes these engines desirable for swapping is their fully mechanical injection pumps, which require no electronics from the truck to make the engine run. This simplicity makes the 12-valve Cummins the easiest install. Simple to maintain, it’s one of the most dependable Cummins engine swaps.

However, the 12-valve Cummins also offers the least amount of factory power and torque, making just 160 horsepower with 400 pound-foot of torque in its earliest form. It also has the least aftermarket support when it comes to performance parts. And its relatively low 2,500rpm redline makes for a unique driving experience.

Engines offered from 1989 to 1993 utilized Bosch VE rotary-style injection pumps with fuel pins to control flow and until 1991.5 came without intercoolers. Adding an inexpensive high-flow fuel pin can achieve an increase of 40 to 60 horsepower, which would make having an intercooler desirable. In 1994 the engine was updated to a newer Bosch P7100 injection pump with a plate to regular fuel flow. Like the VE pump, adding a simple aftermarket fuel plate to the P-pump can boost output between 15 and 95 horsepower. The later P-pump 12-valve Cummins engines offer slightly better aftermarket support and are more adept at making higher horsepower. However, they are still quite limited by the nature of mechanical fuel injection.

1998½ – 2002: 24-Valve 5.9-liter Cummins

In mid-year of 1998, Cummins released an all-new version of its 5.9-liter diesel engine. Commonly referred to as 24-valve engines, these new mills now featured four valves per cylinder (two intake and two exhaust), hence “24-valve.” Power output increased to 235 horsepower with 460 pound-foot of torque during this engine’s short run. A Bosch VP44 injection pump provided fuel to the injectors. The engine’s redline saw an increase as well to 3,200rpm, which offered far greater drivability.

Unlike the 12-valve Cummins engines, these 24-valve mills came with computer control. It is imperative to ensure that the Dodge PCM and Cummins ECM years match, as many issues have been found when they don’t. That said, the experts at Diesel Conversion Specialists do offer a standalone harness for the 24-valve Cummins that will enable it to run in any chassis by simply adding 12-volt power and ground.

It’s not all roses, though, as this generation engine suffered from the “53” block issue. Engine blocks cast with “53” just above the oil pan rail on the driver’s side have been known to crack at the exterior water jacket. It’s also necessary for later 2001 to 2002 engines to have an electronic speed signal from the vehicle in order to run correctly. The thermostat housing also points to the driver’s side of the truck, which poses an issue when installing [the engine] in a Ford chassis.

 

2003 – 2009: Common Rail 5.9-liter & 6.7-liter Cummins

One of the biggest advancements in Cummins engine technology happened in 2003 as the engine swapped from mechanical fuel injection to a high-pressure common-rail fuel system. The “common-rail” refers to a central, high-pressure fuel rail on the inline engine in which the electronic injectors connect, instead of a spiderweb of hard lines. In 2007, Cummins increased the displacement from 5.9 liters to 6.7 liters.

These common rail Cummins engines are among the most popular when it comes to swaps because they offer great power and reliability, are fairly common and not overly expensive to source, and engine tuning and upgrades are plentiful. Not all common rail Cummins engines are equal, however.

First, it’s important to note if the ECM that came with the engine is from a manual or automatic transmission-equipped truck. Some people say the manual transmission ECMs are more desirable, as they are easier to tune. If the donor truck had a key-recognition security system, the ECM will need to be reflashed to remove any software locks. And the original accelerator pedal position sensor will likely need to be retained as well. Thankfully, the totally integrated power module (TIPM) is not required for engines from 2006 to 2009.

 

 

2010 – 2012: Common Rail 6.7-liter Cummins

The 2010 to 2012 RAM 6.7-liter Cummins engine is largely the same as the previous common rail model. Additionally, in 2011 the company began offering a high-output version that produced 350 horsepower with 800 pound-foot of torque. These engines, while also the most complex when it comes to wiring, offer the greatest power potential while retaining all their factory-installed emissions equipment, for those for whom that’s a concern. This swap is best undertaken by someone highly experienced with diesel engines, wiring, and tuning.

Engines newer than 2012 are not recommended for swaps due to the complexity of their emissions control systems. In addition to exhaust gas recirculation (EGR) and a diesel particulate filter (DPF), these engines were also fit with selective catalytic reduction (SCR) and require the use of diesel exhaust fluid (DEF). Modifying these engines to work outside of the RAM truck chassis is prohibitively difficult.

 

ISB Industrial Cummins Engines

We know what you’re thinking and yes, Cummins has built many more engines other than just the 5.9-liter and 6.7-liter engines used by Dodge and RAM. And while the prospect of picking up one of these bread van powerplants cheap at the pick-n-pull might sound enticing, it’s worth knowing that the company’s commercial ISB engines (the ones painted red) are entirely different animals. Often these engines are tuned to run at a single engine speed (or at a much lower RPM than typical pickups would). Also, the cost and complexity of retrofitting these engines for service in pickups can prove to be insurmountable.

The list of details that differ between the pickup and industrial engines includes (but is not limited to) injection pumps, timing covers, turbocharger inlet and outlet, throttle linkage and cables, oil pan and pickups, exhaust manifold, front accessory drives, and electronic controls with no or limited tuning control.

 

Good luck on your Cummins engine swap!