I did a search but I don't know how good it was.
Last year - more like 18 months + ago I had to replace the lifters in my G8GT due to a failure at 162K miles. Today I have 166K miles or so, and when I did the update I got new lifters, a LS3 Hot Cam, new springs and other pieces. ripped it all out - got it roughly tuned - still needs work there. And it's run fine since.
fast forward to last week.
cold start
clacketa, clacketa, pause clacketa clacketa . . . . . Grand. Seems to be DR Side - and I think it's from the front end but hard to say. goes like this for a bit - rhythm changes , sound level drops a bit - and gone.
If left to sit 6+ hours - it does it again. SO reading various things I decide - I might should change the oil a touch early. filter might be bad who knows.
OIl change - using a high mileage based oil now (pennzoil platinum at the time); and after that oil change start up which did clack for a bit.
Next day cold start - much much quieter but still there a bit. 2-3 days same thing light to almost nothing. Then 2 days no extra noise. great. but it was also 70 in the morning and 90 that afternoon. (thanks fall)
Today dropped to 40 last night - was 52 when I remote started. louder - clacketa, clacketa . . . . went for 20-30 seconds settled into a constant clack - minute or so quieted down significantly. then gone again.
Other tests - oil pressure after start seems to run at or near 42 psi. once fully warmed up it stays around 42 at idle. I traded the oil pump when I did the other work for the high volume pump - and also did the DOD delete.
2 thoughts - pushrods are a worn to be a tick too short - say 0.001 off give or take. or Dirt still in the oil paths to the lifters? I'm leaning towards the first one.
If I can get it to do it - I bet the clack noise drops off as soon as the coolant temp starts to register and it disappears before it reaches normal. IE engine up or over 130 degrees. This leads me to think it's the pushrod length issue. But I hear supposedly a large number of LS3's make cold start valve train noise. So I don't know.