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Old 12-11-2020, 08:44 AM
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taff2 taff2 is offline
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Join Date: Sep 2005
Location: South Wales in UK.
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The old rule of thumb was .001" clearance per inch of journal diameter, so in your case a minimum of .00325" . I've run .003" -.0035" clearances on a n/a factory cast crank/block combo to 7000rpm, and .0035" clearances on my Scat 3.00" journal crank/factory block turbo combo to 7000rpm , bearings always looked good on strip down. Cold oil pressure was always around 80-100, hot it drops down to 20-30 at idle, Valvo VR1 20/50. Besides the extra clearance allowing more oil to pass through the bearings keeping them cool, it also allows a margin of safety when the crank flexes (and they do) at high power/rpm, so that the crank doesn't nip the bearing. JMO

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