The knocking could be your timing device slamming back and forth if the brass bushing in back of the timing device is warn. Its easy to check for this problem, grab hold if the timing device and make sure there is almost NO lateral movement. There was 2.5 mms in the one I had that destroyed the VP of a 240D of mine. I didn't hear it run but I'm betting there was some noise. That engine was in a burned out parts car and was said to be good but I pulled the VP just to check it and found the damage before the ball bearings came adrift.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"