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Ram Cummins ISB 6.7 specs: 408 ci (6.7L) 6-cylinder, 4.213 x 4.882 in (107 x 124 mm) bore and stroke. Rated 350-370 hp, 2007–2024.
The Ram Cummins ISB 6.7 is undersquare — the 4.8819" stroke exceeds the 4.2126" bore by 13.7% — a layout that trades peak RPM for leverage and torque low in the range. With a 4.8819" stroke, mean piston speed reaches 4,000 ft/min at only 4,900 RPM — the practical ceiling for a production bottom end — which is why a stroke this long makes its power low and runs out of safe revs early. Each of the 6 cylinders displaces 68.0 ci (1,114 cc).
It is one of 5 engines in the Cummins ISB family, all of them 408 ci — the differences between them are in compression, heads and rating, not displacement. 18 factory variants share these dimensions, rated from 350 to 370 hp across 2007–2024.
| Displacement | 408 ci / 6.7 L |
|---|---|
| Bore | 4.2126" |
| Stroke | 4.8819" |
| Cylinders | 6 |
| Configuration | I6 |
| Bore/stroke ratio | 0.863 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | diesel |
| Advertised HP | 350–370 hp |
| Years | 2007–2024 |
| Bore/stroke character | 0.863 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 4,882 ft/min — above the 4,500 ft/min mark where most production bottom ends are considered at their limit |
| Displacement per cylinder | 68.0 ci |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 2007 | 350 hp | Cummins ISB 6.7 |
| 2008 | 350 hp | Cummins ISB 6.7 |
| 2009 | 350 hp | Cummins ISB 6.7 |
| 2010 | 350 hp | Cummins ISB 6.7 |
| 2011 | 350 hp | Cummins ISB 6.7 |
| 2012 | 350 hp | Cummins ISB 6.7 |
| 2013 | 370 hp | Cummins ISB 6.7 |
| 2014 | 370 hp | Cummins ISB 6.7 |
| 2015 | 370 hp | Cummins ISB 6.7 |
| 2016 | 370 hp | Cummins ISB 6.7 |
| 2017 | 370 hp | Cummins ISB 6.7 |
| 2018 | 370 hp | Cummins ISB 6.7 |
| 2019 | 370 hp | Cummins ISB 6.7 |
| 2020 | 370 hp | Cummins ISB 6.7 |
| 2021 | 370 hp | Cummins ISB 6.7 |
| 2022 | 370 hp | Cummins ISB 6.7 |
| 2023 | 370 hp | Cummins ISB 6.7 |
| 2024 | 370 hp | Cummins ISB 6.7 |