I own a 2002 gmc 1500. It has the 4.3 v-6 engine. The truck is driven very lightly and has only about 60000 miles on it. The problem is when you go to start it, it ticks very obviously. It sounds like it is coming from the valves. It only taps for maybe 15-45 seconds. Then it goes away completely. Anyone know what is causing this and how i could fix it? the truck runs fine other than that..

 

I've got the same sound upon cold start with my '02 5.3

Get's worse when you give it gas, so I try to let her idle a bit before getting moving.

It's been explained to me as "Piston Slap", but I'm not sure how credited that explanation really is. Either way, doesn't sound good, but it's been doing it for years and I'm up at 156,000 now with no major probs, fingers crossed/knock on wood!
ALso, not sure if this is the same noise you are explaining, or even if it's related to the 4.3l. I had a '99 Sonoma with a 4.3, and I don't ever recall hearing any ticking or "piston slap".