COULD BE A WRIST PIN
I HAD AN 88 TBIRD WITH 5.0 WITH LOTS OF BOLT ONS THAT WOULD KNOCK BUT IT WAS QUIETER THAN A ROD KNOCK
AND WHEN IT GOT WARMED UP IT WENT AWAY
I DROVE THE S*** OUT OF THAT CAR FOR 5 YRS TILL I GOT SOMETHING NEWER
NEVER HAD A PROB. BUT THAT MAY NOT BE YOUR CASE...