I have a knocking sound only at idle I changed rod bearings no change I took it to a mechanic and they said timing chain so I had them do it now they call and say it's quieter but still has a knock at idle only does anyone have any info that might help me

 

Knock at idle in the past indicated a main bearing knock. The 4.2L being a push rod engine with cam in block, the older knowledge usually applies to it.