Hey yall, I recently installed a new timing chain with a new water pump as well, and went to start my car up for the first time today and it started fine and revved up fine with no noticeable issues, my problem is as soon as my car gets below 750 rpm’s a very loud rattling and clunking noise begins. It’s doesn’t seem to happen until I’m below 750 RPMS, sounds like the chain is slapping against something, but I’m not positive.I really don’t want to tear everything down again but I might have to. Anyone have any ideas why it could be?

 

It would be easiest to check things that are most accessible.

Have you removed the belt(s) to determine if it's an accessory noise?

Is the harmonic balancer fully installed and running true? Are its outer ring and rubber isolator intact?

 

If it didn't make the noise before and it does now, Occam's razor suggests that something you reassembled is not quite right. Could be as simple as a loose belt, fan shroud, or misalignment of an accessory. Check over everything, use a straight edge on the pulleys, remove the belt and spin all the accessories by hand, use a mechanic's stethoscope to isolate the area of the noise and worst case start the project over.