Knocking, as in mechanical clunking or as in ignition pinging?

The timing gears are the achilles heel of the B18/B20 motors, I think often the B30 got a steel timing gear set but it could still be the culprit. At idle and low speeds a bad timing gear can sound like an idling semit truck diesel motor. It can sound just like a rod knock, only a timing gear will often quiet down as the rpms rise, but rod knock can happen at any rpm if the piston loading is right (often when the rpms are falling, on the 'overrun').
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