[CT Jack]

The knock sounds familiar and my guess is the timing gear is worn. You can do a simple test to identify if it is the timing gear. Remove the timing pin on the bottom front of engine. Start the engine and slowly insert the timing pin into the timing hole with the rounded end of pin. Push the pin against the cam gear and if the knocking noise changes, gets softer this means it needs to be replaced. Usually the wear occurs on the ID of the gear or the nut can come loose creating excessive backlash.