440 Six Pack Main Bearing Clearances: Journal and Bore Sizes
The 440 Six Pack or 6-BBL main bearing clearances, main journal and bore size is often asked. Let’s take a close look at each one.
The 440 Six Pack desired main bearing clearance for 1969-1970 is .0005″-.0015″ and .0005″-.002″ for 1971. The maximum allowed clearance is .0025.” The main bearing journal diameter is 2.7495″-2.7505″ and the main bearing bore size is 2.9425″-2.9430.”
This article will take a deeper dive into the details of each year. In addition, I’ll include the factory desired and maximum clearances and other main bearing specifications.
440 Six Pack Main Bearing Size
When making purchases, checking clearances or just curiosity, you may want to know the factory specifications.
The 440 6-BBL or Six Pack main bearing journal and bore remain the same for all three years. There are differences in bearing material and clearances between the years. Those differences are shown below.
The main bearings may be a small engine part but they’re important and is anything but small. Let’s examine the main bearing journal first.
440 Six Pack/6-BBL Main Bearing Journal Size
The main bearing journal size is the diameter of the main bearing journal on the crankshaft.
- The 440 Six Pack main bearing journal diameter is 2.7495″-2.7505.”
- The maximum allowable out-of-round and/or taper are .001″
440 Six Pack 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 440 Six Pack main bearing bore size is 2.9425″-2.9430.”
440 Six Pack Main Bearing Clearances
The main bearing clearance refers to the space between the outside diameter of the crank journal and the inside diameter of the main bearing.
The space or clearance allows a cushion of oil between the journal and bearing.
When checking the main bearing clearances on your Six Pack or six barrel, two tools are required:
- A dial bore gauge to measure the inside diameter of the main bearing.
- A micrometer to measure the main bearing journals.
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.
Disclaimer: Some of the links in this article may be affiliate links. As an affiliate associate, I may earn a commission for qualifying purchases at no extra cost to you.
Check out quality dial bore gauges and micrometers at Jegs High Performance, Dial Bore Gauges and Micrometers.
1969 Crankshaft/Main Bearing Specs and Clearances
- Type: Fully Counter-Balanced
- Bearings: Steel Backed Babbitt
- Thrust Taken By: #3 Bearing (Thrust Bearing)
- End Play: .002″-.007″
- Maximum Allowable: .010″
- Clearance Desired: .0005″-.0015″
- Clearance Allowed: .0025″
1970 Crankshaft/Main Bearing Specs and Clearances
- Type: Fully Counter-Balanced
- Bearings: Steel Backed Babbitt*
- * #3 Bearing is Tin Aluminum Alloy Steel Backed
- Thrust is taken by the #3 main bearing (Thrust Bearing)
- End Play: .002″-.007″
- Maximum Allowable: .010″
- Clearance Desired: .0005″-.0015″
- Clearance Allowed: .0025″
1971 Crankshaft/Main Bearing Specs and Clearances
- Type: Fully Counter-Balanced
- Bearings: Tin Aluminum Alloy Steel Backed
- Thrust is taken by the #3 main bearing (Thrust Bearing)
- End Play: .002″-.007″
- Maximum Allowable: .010″
- Clearance Desired: .0005″-.002″
- Clearance Allowed: .0025″
These are tight clearances but remember the factory often recommends a tighter clearance than race engines.
If you have any questions about the Six Pack main bearing clearances, journals, posts or more information you’d like to contribute, send us an email found specifically on our contact page.
More Main Bearing Articles
For the past 40 years, I’ve been studying and researching Mopar engine specs like the 440. Six pack I’ve assembled 440 Six Pack engines, read books, articles, magazines, watched videos, attended seminars and spoken to other Mopar experts about the topic.
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440 Six Pack Compression Ratio
Article Resources
- Mahle: Performance Engine Bearings
- Mahle: Chrysler Bearings
- Google Books: Chrysler Engines 1922-1998
- Chrysler Service Manuals: 1966-1971
