Crank and babbitt bearing wear question

[Special Coupe Frank]

I am continuing to check-out my diamond long-block.

Today I mic'd the crank: main and rod journals.

( I mic'd at three different spots along each journal face, in both the vertical and horizontal axes, with the rod throws at TDC/BDC. So I got six measurements per journal.)

The crank has a lot of rust / acid pitting on the journal surfaces, so I am mostly trying to determine if the crank was ever turned at some point.

The stock spec for Main journal is 1.6240". Actual: 1.6108". Variance: 0.0132" ( "13 thou" )

Stock spec for Rod journal is 1.4990". Actual: 1.4530" Variance: 0.0460" ( "46 thou" )

Note: for this exercise, I averaged the measurements of the mains, and then the rods.

To my little mind, it would seem as though this crank has been cut, its Mains turned 0.10" under, the Rods turned 0.040" under, and the rest is wear ?

There were no shims left in any of the bearings.

How much wear take-up can one expect to get from a Babbitt bearing over its working life ?

Thanks!

Frank

[Special Coupe Frank]

Well, I think my metrology tools are pretty decent: L.S. Starrett outside micrometer, which reads to ten-thousandths (four decimal places ), I don't know about my methods for sure, in terms of where I measured the journals; but for purposes of trying to figure-out whether or not the crank was still at stock dimensions or if it had been machined during its life, I'm pretty confident it's had work done.

Also found "piston expander" clips in the slots of the piston skirts, so it seems likely that this particular engine has seen some work in the past.

I have a crank from a '29 engine whose journals are definitely cleaner, don't know yet if their size matches the diamond block or its rods.

At this point, trying to assess the over-all condition of this engine, whether it will run a couple thousand miles as-is, or if it's really ready for rebuild. (My wallet isn't ready for that, but I don't want to swap a time-bomb into my car either.)

Thanks,

Frank

[Mike V. Florida]

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Originally Posted by Special Coupe Frank

Also found "piston expander" clips in the slots of the piston skirts, so it seems likely that this particular engine has seen some work in the past.


At this point, trying to assess the over-all condition of this engine, whether it will run a couple thousand miles as-is, or if it's really ready for rebuild. (My wallet isn't ready for that, but I don't want to swap a time-bomb into my car either.)

Thanks,

Frank

Originally Posted by Special Coupe Frank

So I got six measurements per journal.)

The crank has a lot of rust / acid pitting on the journal surfaces,...

There were no shims left in any of the bearings.

I know what it is like not to have spare cash for your car, I really do. I also know the need to drive the A as a method of mental health, But I think you answered your own question.