The Clanging noise happens when i start the Car..79.12a. stock except for RB .headers.This car is a AUTOMATIC.THE sound is similar to a loose muffler vibration somewhat of aSHRILL sound not a DEEP sound..IT only does this after after starting and stops about 3seconds after start..No sounds while driving,idiling,ETC...SOUNDS like it is under your feet (if theres a guess area)..SO if anyone has any KNOWLEDGE PLEASE share your thoughts..THANKS

 

start simple. check for loose or broken mounts. also look to see if any of the exhaust shielding (assuming you still have any) is bent or loose.