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Possible sources of a knock at idle is;
Excessive crank endplay at #1 bearing
Excessive gear lash between the intermediate gear and the crank gear.
Porsche made a batch of 3.0 liters that had excessive crank endplay and exhibited a knock below 900 rpm
They were replacing engines under warranty until they figure if they increased idle rpm above this, the knock was not present and “fixed” the complaint.
The likelihood of either of these conditions has increased as age and the subsequent wear on both of these parts iirc, spec is .004” for endplay. The cranks were out of spec and had .006-.008 of endplay.
If you are positive that you do not have any tolerance issues and your oil is clean of debris, increase idle speed and enjoy.
Last edited by BURN-BROS; 02-25-2021 at 08:20 PM..
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