The size of the factory 426 Hemi main bearing journal and the main bearing bore size is a question often asked. These measurements are necessary for bearings and clearances.
The 426 Hemi main bearing journal size (diameter) is 2.7495″-2.7505.” The outside diameter of the main bearing or the main bearing bore size is 2.9425″-2.9430.”
This article will explain the measurements in more detail. In addition, it will include the factory desired and allowed clearances and other main bearing specs.
426 Hemi Main Bearing Size
When purchasing replacement main bearings or checking for clearances, you’ll want to know what the factory specifications are.
Main bearings are small but are one of the most important engine parts.
426 Hemi Main Bearing Journal Size
The main bearing journal size is the diameter of the main bearing journal on the crankshaft.
The 426 Hemi main bearing journal diameter is:
426 Hemi Main Bearing Bore Size
The main bearing bore size is the inside diameter of the main bearing housing without the bearings installed. It’s also the outside diameter size of the main bearing.
The 426 Hemi main bearing bore size is:
426 Hemi Crankshaft and Bearing Specs and Clearances
426 Hemi Crankshaft and Bearing Factory Specifications:
- Type: Fully Counter-Balanced
- Bearings: Steel Backed Grid Type (1966)
- Bearings: Tri-metal Steel Backed (1967-1971)
- Thrust: Number 3 Main Bearing (thrust bearing)
- End Play: .002″-.007″
- Maximum Allowable: .010″
- Main Bearing Journal Maximum Allowable Out-of-Round: .0003″
- Main Bearing Journal Allowable Taper: .0005″
The factory crankshaft and main bearing specifications remained pretty consistent for all years from 1966-1971.
There is two exceptions for bearing type in 1966 and the clearances in 1971 shown next.
Main Bearing Clearances
The following are the 426 Hemi main bearing factory clearances for each year:
Main Bearing Desired Clearance
Main Bearing Maximum Allowed Clearance
If you’re interested about how emissions affected timing check out my article, 426 Hemi Timing.
Main Bearing Clearance: How to Check
When checking the main bearing clearances on your 426 Hemi, two tools are required:
- Micrometer to measure the main bearing journals.
- A dial bore gauge to measure the inside diameter of the main bearing.
The main bearing journal diameter can be checked with a precision micrometer sized for the range of the journals you will measure.
There are many cheap micrometers out there for sale you should avoid. Use a quality micrometer that will measure down to the 0.0001-inch.
Also, the best dial bore gauges are accurate down to 0.0001-inch. The two tools can be purchased as a set offering measurements from the 2-4″ range.
For most street/performance engines, most crankshaft manufacturers recommend 0.010″ clearance for every 1″ of journal diameter.
Therefore, using a 426 Hemi’s 2.75″ main journal as an example.
- 2.75″ x .0010″ = .00275″ clearance.
This is slightly more than the factory service manual and most performance/racing engines use more of a clearance.
Bearing manufacturers sell oversize and undersize bearings for more clearance if needed or desired.
Never mix shell halves of more than .001 inch difference.
Never combine a .001 inch oversize half with a .001 inch undersize. Always use the smaller diameter half as the upper.
If you’re interested in the connecting rod journal size and specs, check out my article, 426 Hemi Rod Journal Size.
Check the factory torque specs for the main bearings in my article, 426 Hemi Specs.
If you have any questions about main bearings, posts or more information you’d like to contribute, send us an email found specifically on our contact page.
For the past 40 years, I’ve been studying and researching Mopar engine specs like the 426 Hemi. I’ve assembled engines, read books, articles, magazines, watched videos, attended seminars and spoken to other Mopar experts about the topic.
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