How to check the big end of a connecting rod.

How to check the big end of connecting rods.


The subject rods are from Subaru EJ25 engines
I started out with 19 rods, the 20th rod was junk from being spun so bad.


Commonly the pistons are removed from any connecting rod being checked.


First thing to do is clean the rod of old oil.

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While the rods get washed, I set the Sunned AG-300 to the housing bore size.

The spec is 2.1648-2.1652

The mic is set for 2.165

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Now that the rods are washed

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Each bolt is lubed and installed back in the rod, I use a moly lube.

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After the bolts are hand tight, then are put in a rod vice, with the split of the rod out of the vice.

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Then they are torqued to spec

31-34 ft/lbs

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Once torqed, they are checked for round.

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(The AG-300 reads in .0001 increments, so I am allowed .002 in the red and .002 in the green for the rod to be in spec)


Now to just “shine” the housing bore and remove the hard varnish.

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On the machine.

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How it looks after the shine. Yes it gets another check after this to make sure it is still in spec.

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Next is to bump it on a belt sander to shine the sides.

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Then they go back to be washed again, to remove the hone oil and grit. Then they are ready to go back in service.