You may be dealing with tow different kncoks. One sounds like piston
slap/knock when engine is cold and the other sounds like rod knock when
engine is warmed up. It could be a very loose piston the knocks all the
time too. A rod knock and startup would not fade away after a minute or
so but piston slap can as it swells from heat.
I got an idea go to tools, options, click on the tab (spelling), check the
box that says always check spelling before sending!!
Now to answer your question, if it is a 5.7 or 6.0 V-8, or 4.3 V-6, and it
was build on or after 1994 you probably just have piston slap. This gets
noisier at about 1500 rpm, but it usually goes away when the engine is
warmed up. If yours doesn't go away, or gets louder it is probably a rod
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