[34Pietenpol]

Thank you. The sound builds as rpm increases and it often will recur when decelerating. The sound definitely gets more noticeable when the engine warms up. The oil was changed into an open pan and inspected visually for metal pieces. It was not sent out for analysis though.

From Andrews troubleshooting and the probable location between 2 and 3 it does sound like the center main is the culprit. I have no history on the rebuild of this engine. I’ll drop the oil pan, see if there are shims in the bearings, check bolts, see if removing shims will help. Will be able to see what’s in the bottom of the oil pan as well.