We can rule out the A/C compressor. I don't have one!

I am beginning to think that this is more or less an injector knock. I have driven this thing very hard today trying to get it to throw a rod. I have floored it while parked. I have romped it numerous times. It will not make this noise unless it's under load accelerating and at speeds of 50 to 55. It is not a constant rattle or knock. It is intermittent, rather sporadic. Sometimes when I take off it is never heard. Other times it is heard for a few seconds, goes away, returns but never gets any louder. I do not hear it at highway speeds. At idle it sounds so nice and smooth. It has got to be something about the timing. I will find out tomorrow because I am going to set it back close to where it was before I messed with it.

As far as a stethescope- It only knocks while driving. It will not knock at idle. My wife refused to ride on the hood to help me diagnose the knock!

I have tried to throw a rod today just to see if it is a rod knocking. The bottom end seems rather tight. I have slammed it into passing gear many times today and revved it to the max but cannot throw a rod.

I did remove the # 1 prechamber today just out of curiousity. It was fine, at least I think it was. Nothing broken in there.

Kevin