I'd like to know who at GM told you that it was the "aluminum pistons" making the noise? Since virtually all automobile engines have aluminum pistons.

With about 200,000 miles on that 5.3L powerplant there is surely a fair amount of wear and deposit accumulation in the motor. A ticking noise for a short period following start-up is normally caused by a delay in lubrication reaching the valve-train due to worn components or a lifter that is bleeding down also from normal wear and tear.
My opinion is that the noise most certainly will not result in a catastrophic engine failure so I would wait to make a repair until it comes time for an overhaul.

 

I have the same problem with my 99 Silverado. I heard that it was common with the 5.3L Vortec. They (GM) called it piston slap caused by carbon build-up between piston and head. They said there is nothing you can do about it, but it's not a problem. Funny they would say that!

 

Mine does it too, especially on cold days. I have a 99 with 77K on it. I've heard that GM excuse before. But then again, my steering shaft clicks, my leaf springs squeek, and my exhaust rattles and they told me the same thing about those noises too. (With the exhaust it was mismatched washers/spacers on the o2 sensors being loose and rattling supposedly from the factory, sigh, I hate GM sometimes).

 

The old Y Block Fords were known for the ticking from the exhaust manifolds. Didn't sound like a leak. It sounded like a lifter ticking till it warmed up or you tightened the manifold bolts. They didn't use exhaust manifold gaskets. I had a couple of them.

 

My 08 with the 5.3 also does it. I have 21,000 miles on it.

My 02 Dodge Caravan with 80,000 miles also does it, so I'm not worried.

 

I change oil every 3k 10/30 or 10/40 in summer usally a name brand pennsoil/valvoline standard oil

 

Does anyone think Lucas oil treatment could help this situation? Please help!!

 

Lucas prob won't help but you can try. I'd use the normal stuff for >100K, else I'd use the synthetic Lucas for <100K.

 

using 5w-30 motor oil?.. bad idea in an old engine try running 10w30 synthetic.. but always run sythentic from now on...

 

Thanks guys!!!