One guy thought it was a piston going bad because of the noise and needed a engine. Another guy said the car isn't smoking, losing power,losing compression,losing oil pressure, or radiator fuild and thought it was a valve problem. He said it seem the noise was moving a little under the manifold. Any thoughts or suggestions to find out the proble for sure?
My son's impala started to make a knocking noise. on 2003 Chevrolet Impala
Get a wooden stick that is small in diameter and long enough to reach down to various places in the engine compartment. Put the tip of the stick in various places or where you think the noise is. What you are doing is using the stick as a steth-a-scope. Put the other end of the stick against you ear and you should be able to figure out where the noise is coming from and what is causing the noise.
Find a tech that has lots of experence in engine repairs to listen to it. Ask around say at local parts stores for someone that is known in your area as an expert in engines and get their opinion.