notice that he is talking about two different sounds. the first one is what everyone is talking about as the timing chain.
but the second one, the sounds you are hearing when going up hill under load are probably caused by detonation (what some are calling pre-ignition, though they are really two different phenomena) in the cylinders. detonation occurs in the cylinder after the spark plug fires due to excessive heat and pressure and the fuel not being able to resist detonation. the sound you hear is the engine ringing, and is commonly called ping or spark knock. here is a link with a lot of info on detonation and pre-ignition:
http://www.streetrodstuff.com/Articl...ne/Detonation/
some things that could cause it:
1. engine timing advanced too far
2. lower octane fuels
3. faulty EGR valve leading to higher temps in the engine
