440 Rod Journal Size: Bore Sizes and Bearing Clearances

The Mopar 440 rod journal size is a question which comes up often. Let’s examine what the 440 rod journal size is.

The Mopar 440 connecting rod journal diameter is 2.374″-2.375.” The rod bearing bore size or outside diameter of the rod bearing is 2.5000″-2.5005.”

This article will explain the journal measurements and sizes in more detail. In addition, it will include the factory allowable out-of-round, taper and crankshaft bearing clearances.

440 Rod Journal Size

Connecting rod bearings are small and relatively affordable compared to other engine parts. It’s definitely not one of the first engine parts talked about. Although they are one of the most important.

When checking for bearing clearances or purchasing connecting rods, knowing the factory specifications are something people should know.

The rod journal and bore size remains the same for all the years. There are differences in clearances. Those differences are shown below.

For the purpose of this article and website in general, this article will concentrate on the “muscle car era.” I’ll examine the 440 from 1966 to 1974.

Let’s take a close look at the rod journal, bore and bearing sizes.

Crankshaft: 440 Connecting Rod Journal Size

The connecting rod journal size is the diameter of the rod journal on the crankshaft. It’s what the big end of the rod bolts on to.

Mopar big blocks have four of them, each one sharing two connecting rods each.

  • The 440 rod bearing journal diameter is 2.374″-2.375″ (2.375″).
  • The maximum allowable out-of-round and/or taper is .001″

440 Connecting Rods: Bearing Bore Diameter

The rod bore size is the inside diameter of the rod bearing housing without the bearings installed. It’s also the outside diameter of the rod bearing.

  • The 440 rod bearing bore diameter is 2.5000″-2.5005″

Rod Bearing Clearance

Two tools are required when checking the clearances on the connecting rod bearings:

  • Micrometer to measure the rod bearing journals.
  • A dial bore gauge to measure the inside diameter of the Hemi rod bearing.

The rod 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.

The Plymouth and Dodge service manuals indicate the following 440 rod bearing clearances for each year:

  • For 1966 the desired clearance is .0005″-.0015″ and maximum allowable is .0025.”
  • For 1967 the desired clearance is .0005″-.0015″ and maximum allowable is .0025″
  • For 1968 the desired clearance is .001″-.002″ and maximum allowable is .0025″
  • For 1969 the desired clearance is .001″-.002″ and maximum allowable is .0025″
  • For 1970 the desired clearance is .001″-.002″ and maximum allowable is .0025″
  • For 1971 the desired clearance is .001″-.002″ and maximum allowable is .0025.”
  • For 1972 the desired clearance is .001″-.0025″ and maximum allowable is .0025.”
  • For 1973 the desired clearance is .001″-.0025″ and maximum allowable is .0025.”
  • For 1974 the desired clearance is .001″-.0025″ and maximum allowable is .0025.”

Remember, higher performance engines require more bearing clearance than factory stock. The following video describes that plus bearing information.

The video explains how to measure the rod journals.

If you’re interested in the main bearings journal size, bearings and clearances, check my article, 440 Main Bearing Size.

If you have any questions about rods, bearings, posts or more information you’d like to contribute, send us an email found specifically on our contact page.

How to check rod and main bearing journals and clearances.

More Rod Journal Articles

For the past 40 years, I’ve been studying and researching Mopar engine specs, rods and bearings like the 440. I’ve assembled 440 engines, read books, articles, magazines, watched videos, attended seminars and spoken to other Mopar experts about the topic.

Read More 440 and Mopar Engine Articles!

The Deck Height of a Mopar 440

440 Firing Order

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