[QUOTE=Bluegrass1985;233278]What is rod bearing clearance for a Cat thirty. I have it at 3thou on three cylinders. Have not installed the fourth. Just installed new rings. Bore is decent. Seems a little tight when cranking. Noticeable difference when I back off nuts. Wondering if it’s a little tight. Thinking of adding the one shim I removed on each side. Need some opinions.
Have you checked the roundness of the journal? That helps to know because the book says to measure clearance by movement. If it moves more than .012" remove shims evenly. It should not have less than .003" movement. I use a dial indicator and check in different places account for out of round journals.
Its a bit of a balancing act on a old engine when the crank is likely worn egg shape, 003 is tight in my book.
My thoughts
-is there a ball-park spec for clearance?
-my limited automotive engine building...rule of thumb....approx .001" clearance per inch journal diameter..? and that may be a bit on the tight side...you can definitely add to that and be looser with no problems..assuming pump is adequate ect...
My personal spec. is .003-.006. older style engine wide bearings, slower RPM and 30wt oil.
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