LS3 18000 miles Ticking Cold Start commonly referred to as Piston Slap
 

Just bought a 2012 with 18000 miles. On cold start I pick up a ticking noise. When driving the tick speeds up, Hear it for about 1 mile. If I let it idle and warm up then drive it there is no ticking. When warm no noise at all. Long story short from what I see this is normal on the LS3 and even have read on the later model cars. I don't know if the true name is piston slap but told this is normal. THXXXXXXX in advance.

Yes, LS-3s are known for having noisy valve trains. Most likely its your lifters and is normal till warmed up.

My LS2 does it also, mine only does it for about 20 to 30 seconds after start up, then goes away.. Once it does it at startup it never does it again for the rest of the day..It could also be one of your lifters is bleeding down over night and needs to pump back up, piston slap is more of a mild knock then a tick...Both of these noises can happen with LS engines and shouldn't be a problem unless it's severe, or it doesn't go away after warm up.. .WW
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Perfectly normal! My 08 LS3 does it. It's got 25K miles on it.

The 6 liter truck motor is notorious for this. Piston slap. Google it.

My LS7 does it, as well as two other LS7 powered cars I've driven.

For the record my mustang with the 5.0 Coyote did this too and it drove me nuts but apparently was fairly normal.