The Cummins 4BT and Cummins 6BT are two of the most widely used diesel engines in the world. Both belong to the famous B-Series family and share the same 102 mm (4.02 in) bore, so many owners wonder: what is actually different, and can I use the same parts? This guide answers both questions.
6BT vs 4BT: Quick Comparison
| Specification | Cummins 4BT (4B3.9) | Cummins 6BT (6B5.9) |
|---|---|---|
| Displacement | 3.9 L | 5.9 L |
| Cylinders | 4 inline | 6 inline |
| Bore × Stroke | 102 × 120 mm | 102 × 120 mm |
| Power range | 60–170 hp | 160–325 hp |
| Typical use | Agri, forklifts, small gensets | Trucks, buses, marine, gensets |
Do the 4BT and 6BT Share Parts?
Yes — this is one of the best things about the B-Series. Because the bore and stroke are identical, pistons, piston rings and cylinder liners are interchangeable between the 4BT and the 6BT. Gasket sets are partially shared, while components that depend on engine length — crankshafts, camshafts, blocks — are different.
We stock combined kits that fit both engines, such as the Cummins 4BT/6BT Piston and Ring Kits 3802100.
Which Engine Is Right for You?
Choose the 4BT when space and weight matter and you need under 170 hp. Choose the 6BT for trucks, buses and marine duty where torque and reliability at higher power are required. The 6BT’s inline-six design runs smoother and is the first choice for gensets above 80 kVA.
Common Wear Parts and Overhaul
Both engines wear in the same places first: pistons and liners, then head gaskets, then bearings. For a full rebuild, a complete kit is the most economical way to buy:
- Cummins 6BT5.9 Engine Rebuild Kit OH3802100
- Cummins 6BT Engine Cylinder Block 3903797
- Browse all Cummins 6BT Parts
Get the Right Parts at the Right Price
EPID supplies 4BT and 6BT pistons, liners, gaskets and overhaul kits to Latin America, the Middle East and Africa. Send us your engine serial number or the OEM part number and we will quote within 24 hours.
Contact us or reach us on WhatsApp for a fast quotation.
