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Rod bearing clearances


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5:18 AM
Jul 24, 2013
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I’m currently measuring out my rotating assembly from 440 source. So far my rod bearing clearances appear to be 0.0024-0.0028, measured with a ten thousandths rated micrometer and dial bore gauge. I know the rule of thumb is 0.001 per inch of journal, which for my 2.2” rod journal should be 0.0022 for a minimum clearance. I understand people usually go a bit higher on performance or boosted/high rpm stuff.

What is the max clearance for a street strip build? Is the 2-6 thousandths extra clearance just right or too much? I’m assuming it’s good to run, and a bit of extra is better than too little. But it’s my first build, so I figure I’d run it by some people more experienced than myself.
It’ll run. I Usually shoot for .0024-0026 on rods with a Chevy journal steel rod. If you have something flat like a surface plate you could lap the rod cap on some 320 grit using wd40 to tighten up the loose ones a touch. Other option to to half shell the bearing with some .001 unders. Other words use a standard on one side and the .001 under on say the cap. That’ll probably tighten it too much though. Are all the crank journals measuring exact? I swap the rods to fit the journals sometimes cause they are never all the same just to try to balance the clearances.
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I'm not a builder, but if you .0024-.0026 sounds good for a 6000-6500 RPM motor. On my 7000 RPM motors I was shooting for .0028.
Better a little loose than tight. Your numbers are fine. I've run them as loose as .004". Tightening them to .003" did absolutely nothing to increase the oil pressure. Ran the motor to 7200 for years at .0028"-.003". Bearings always looked great at inspection. Ran 5w30 synthetic.
Your good to go with those clearances. You could reference the FSM for the established range. Even 0.0005" more clearance than the established max tolerance won't be an issue. 440'
I run my 505" stroker at .0024" rod and .0028" main bearing clearances at 6500 quite a bit with no issues. I think you are good to go no problem.