01 Silverado Knocking

Sounds like a lifter leakdown problem when the lifters are gone the camshaft follows or you can mike it out to check- their brothers same goes with the cap and rotor on the ignition system

This is probably the piston slap that as soon as you start the engine. It gets warms agd goes away. A lifter noise will last for about a minute then go away. These models had apiston slap problem. It is nothing to worry about.