Product Description
Interstate-McBee M-4955857 Main Bearing Set – .020" (0.50 mm) Undersize — 1989–2018 5.9L / 6.7L Cummins
Premium aftermarket main bearing set for Cummins B-Series 5.9L (12-valve & 24-valve) and 6.7L engines. This set is .020" (0.50 mm) undersize for use with crankshafts that have been ground 0.50 mm under standard on the main journals. Complete set for one engine; includes thrust bearing halves.
- Correct undersize: For crankshafts ground .020" (0.50 mm) under on mains.
- Complete set: Main bearing shells for all journals, plus thrust bearing position.
- Reliable replacement: Interstate-McBee quality for OE-level fit and service life.
- Service tip: Always measure journals and confirm clearances before installation.
Specifications
| Brand | Interstate-McBee |
| Part Number | M-4955857 |
| Size | .020" undersize (0.50 mm) on main journals |
| Engine Family | Cummins B-Series 5.9L / 6.7L |
| Sold As | Complete main bearing set for one engine (includes thrust) |
| Condition | Aftermarket replacement |
Vehicle / Engine Fitment
Verify by engine serial number (ESN) and journal size prior to ordering.
- 5.9L Cummins B-Series
- 1989–1998: 12-valve (6BT)
- 1998.5–2002: 24-valve (ISB)
- 2003–2007: 24-valve common-rail (ISB CM845/CM850)
- 6.7L Cummins B-Series
- 2007.5–2018: ISB 6.7L applications
What’s Included
- (1) Complete main bearing set, .020" (0.50 mm) undersize
- Thrust bearing halves for the designated main position
Important Sizing Notes
- This set fits undersize crank mains only (journals ground .020" / 0.50 mm under standard). It will not fit standard or .010"/.030" undersize journals.
- Measure the crankshaft and block bore, then confirm oil clearances with Plastigage or micrometers.
- If your crank is standard, order the standard size main bearing set instead.
Installation Notes
- Cleanliness is critical—wash oil passages and blow dry with compressed air.
- Install dry to check clearance; lubricate bearing surfaces during final assembly.
- Align bearing tangs, ensure oil holes/grooves are correctly oriented, and seat thrust halves squarely.
- Torque main caps to the factory specification and follow the correct sequence; recheck crankshaft end-play.
Why Buy From CPP Diesel
- Diesel experts with ESN-verified fitment support
- Fast shipping and competitive pricing
- One-stop source for B-Series bottom-end parts
FAQ
How do I know if I need .020" (0.50 mm) undersize?
If your crankshaft has been ground .020" (0.50 mm) under on the main journals, you need this size. Measure the journals or consult your machine shop.
Does this include the thrust bearing?
Yes, the set includes thrust bearing halves for the correct main position.
Will this fit both 12-valve and 24-valve 5.9L engines?
Yes. It fits 1989–2007 5.9L B-Series and 2007.5–2018 6.7L applications, provided the crank mains are .020" (0.50 mm) undersize. Always verify by ESN.
What if my crankshaft is standard size?
Order the standard-size main bearing set. Using undersize bearings on a standard crank will result in incorrect clearances and engine damage.
