6.7 Cummins Engine Specs Explained: Weight, Cylinders & Diesel Performance
Performance Dodge Blog · Cummins Engine Guide
Inside the 6.7L Cummins
The 6.7L Cummins is the reason many buyers choose a Ram heavy-duty truck in the first place. Yet some of the most searched questions about it are surprisingly basic: what does it weigh, how many cylinders does it have, and how does it compare with a gas V8?
This guide explains the 6.7 Cummins weight, layout, and key engineering specs in plain language, and shows how each one shapes the way a Ram 2500 diesel engine tows, hauls, and holds up over time.
Six cylinders in a straight line give the Cummins its smooth, torque-rich character.
In This Article
Key Takeaways
- ✓The 6.7L Cummins is an inline-six with 24 valves, not a V8
- ✓A commonly cited dry weight is about 1,150 pounds
- ✓Bore and stroke measure about 4.21 by 4.88 inches, for 408 cubic inches
- ✓Since 2019, the block has been made of compacted graphite iron
- ✓The 2025 version makes 430 hp and 1,075 lb-ft in the Ram 2500
How Many Cylinders Does a 6.7 Cummins Have?
The answer is six, arranged in a single straight line. That inline-six layout surprises people who assume a big diesel must be a V8, but it is one of the main reasons the Cummins has such a loyal following. An inline-six is naturally balanced, so it runs smoothly without heavy counterweights or balance shafts. It also uses a single cylinder head, which means fewer parts than a V8 of similar size.
Each cylinder has four valves, for 24 in total. The long stroke, about 4.88 inches against a bore of about 4.21 inches, favors low-rpm torque over high-rpm horsepower. That trait is the real answer behind how many cylinders does a 6.7 Cummins have and why it tows so well. Our 2025 Ram 2500 Cummins specs page also clears up the common V8 question.
Inline-Six vs. V8 at a Glance
A V8 splits its cylinders across two banks and two heads, which keeps it short but adds parts. The Cummins inline-six is longer and taller, and its long stroke delivers torque that gas engines reach only at much higher rpm. Ram’s own 6.4L HEMI V8 makes 405 horsepower but 429 lb-ft of torque in the 2025 Ram 2500, while the Cummins makes 430 horsepower and 1,075 lb-ft.
Engine weight sits over the front axle and affects how much payload is left over.
How Much Does a 6.7 Cummins Weigh?
Published figures for the Cummins 6.7 weight vary with the model year, the accessories included, and whether fluids are counted. Most sources land between roughly 1,100 and 1,200 pounds, with about 1,150 pounds a widely cited dry weight. That is several hundred pounds more than Ram’s gas HEMI V8, and the extra mass comes from the iron block, iron head, heavy rotating assembly, and turbocharger that let the engine survive constant high-load work.
The 2019 redesign switched the block to compacted graphite iron, a stronger material that handles higher cylinder pressures without adding bulk. Even so, a Cummins truck weighs more overall once you add the exhaust aftertreatment system and the heavier-duty transmission.
Why Engine Weight Matters for Payload
Every pound under the hood counts against payload. On a 2025 Ram 2500 4×4 Crew Cab with the 6-foot 4-inch box, Ram rates the HEMI for 3,320 pounds of payload and the Cummins for 2,450 pounds, a difference of 870 pounds. The diesel tows far more, up to 20,000 pounds properly equipped, but carries less in the bed. Our Ram 2500 towing capacity and payload page breaks down every configuration.
6.7 Cummins Engine Specs at a Glance
Here are the core 6.7 Cummins engine specs for the current Ram 2500. Ratings reflect the 2025 High Output engine, while hardware details apply to the 2019 and newer design.
| Spec | 6.7L Cummins Turbo Diesel |
|---|---|
| Layout | Inline-six, 24 valves |
| Displacement | 6.7 liters (about 408 cubic inches) |
| Bore x stroke | About 4.21 x 4.88 in |
| Block and head | Compacted graphite iron block, cast-iron head |
| Turbocharger | Variable-geometry turbocharger |
| Fuel system | High-pressure common rail, up to 29,000 psi |
| Compression ratio | 16.2:1 |
| Output (2025) | 430 hp at 2,800 rpm, 1,075 lb-ft at 1,800 rpm |
| Approximate weight | About 1,100 to 1,200 lbs (roughly 1,150 dry) |
Weight figures vary by source and configuration. Output ratings apply to the 2025 Ram 2500 and 3500.
From the 5.9L to Today’s 6.7L Cummins
The 6.7L replaced the 5.9L Cummins midway through the 2007 model year, largely to meet tighter diesel emissions rules. It added a diesel particulate filter to trap soot, and for the 2013 model year Ram’s heavy-duty pickups added selective catalytic reduction, which uses diesel exhaust fluid to cut nitrogen oxide emissions. Those systems are a big reason the modern Ram 2500 diesel engine runs so much cleaner than the trucks of the 1990s.
The engine itself kept evolving. Output climbed in steps, the 2019 redesign brought the stronger block and a new turbocharger, and the 2025 model year gave every Cummins pickup the High Output calibration. Through all of it, the inline-six layout and 6.7-liter displacement stayed the same, which is why service knowledge carries over so well from one generation to the next.
How These Specs Translate to Diesel Performance
Turbocharging and Fuel Delivery
Specs on paper turn into real capability in a few ways. The variable-geometry turbocharger adjusts its internal vanes to build boost quickly at low rpm, so the engine responds without the lag older diesels were known for. The high-pressure fuel system atomizes fuel finely for cleaner, more complete combustion. Hydraulic lash adjusters, added in 2019, also removed the need for routine valve adjustments.
Towing Response
The payoff shows up when you tow. Peak torque arrives at 1,800 rpm, right where the engine spends most of its highway time with a trailer behind it. Paired with the eight-speed automatic in 2025 trucks, that keeps the Cummins in its sweet spot on long grades. Our look at what changed from the 2024 to the 2025 Ram 2500 explains how the new transmission fits in.
Built for the Long Haul
Durability is the other half of the story. Iron construction, a high-strength crankshaft, and forged connecting rods are why so many owners keep their Cummins trucks for years. Routine care still matters, and our Dodge and Ram maintenance schedule guide covers the service items that protect a diesel.
Is the Cummins the Right Engine for You?
The diesel is not the right fit for every buyer. These pointers help you decide whether its strengths match the way you use a truck:
- Choose the Cummins if you tow heavy trailers often or over long distances
- Consider the 6.4L HEMI if bed payload matters more to you than towing
- Factor in diesel fuel, DEF, and larger oil changes alongside better towing efficiency
- Short local trips suit the gas engine, since diesel emissions systems prefer longer runs
For a deeper side-by-side, read our full Ram 2500 Cummins diesel vs. 6.4L HEMI comparison.
Expert Insight: Check Payload Before You Load the Bed
Buyers focus on tow ratings and forget that engine weight comes out of payload. If you plan to carry a slide-in camper, a heavy toolbox, or a fifth-wheel hitch plus pin weight, read the payload sticker on the driver’s door jamb before you buy. A Cummins truck can still be the right choice, but knowing that number up front prevents an overloaded rear axle later.
See the Cummins Up Close in Woodbury, NJ
There is no substitute for seeing a 6.7L Cummins under the hood and feeling it pull. At Performance Dodge RAM, you can compare new Ram 2500 trucks with Cummins power, browse used Ram trucks for sale in Woodbury, and talk through payload and towing needs with our team.
If you need even more capability, our Ram 3500 research page explains what the next step up offers. You can also schedule a test drive or start with our finance center before you visit.
Bringing It All Together
The 6.7L Cummins is a six-cylinder, 24-valve inline diesel displacing about 408 cubic inches, and most sources put its weight around 1,100 to 1,200 pounds. Those specs explain both its strengths and its tradeoffs: huge low-rpm torque and durability on one side, extra weight and higher running costs on the other. In the newest truck, the latest Dodge Cummins specs read 430 horsepower and 1,075 lb-ft.
For official numbers, fluid capacities, and trim availability, visit our complete 2025 Ram 2500 Cummins specs and engine details page.
Want to See the Cummins in Person?
Visit Performance Dodge RAM in Woodbury, NJ, to compare Cummins and HEMI Ram 2500 trucks, check payload stickers, and take a test drive.
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