They're not "known" for it, atleast not like the early '90s 3.1 Lumina's.
I've heard of some engines having pistons installed backwards (front to rear), which may cause some slap, due to the offset of the wrist pin relative to the cylinder bore.
I think most of the noise that is heard is lash adjusters. Mine are noisy as hell on cold starts, but it goes away within a few seconds. Hopefully that will all change when I install the VT Stage II's!!
As far as piston slap, a dude I know with Bullitt swares he has some but thats all ive heard. I do know that the fuel injectors tick a little loudly at times. I think there may have been a tsb on the injectors but dont remember for sure. Listen to a LS1 on a cold start and listen to your car. Mechanic couple years ago told me most ls1's have it.
Read the whole page looking for the following comment, "While a drilled hole forged piston may exhibit some noise when cold, it would be rare to hear a racer complain about it."
The fact is simply that forged pistons often have noticable piston noise or slap when cold. This disappears as the engine heats up and the piston takes on its round shape.
Note that hyperutectic and cast pistons don't exhibit this characteristic whereas forged pistons do. What does this mean for the 4.6L? It means the DOHC is likely to exhibit more noise at start up than the SOHC. Its no big deal. Its one of the design trade offs in obtaining high performance.
xcessive50, are you talking about a 4V engine specifically. And are talking about a high performance application? I think that article is talking about usages above and beyond our daily drivers.
the car is a 98 gt with 37k totally stock miles on it owned by a lady since 12k.(totally cherry and garaged)She said it has a rattle at 2200 rpm and her mechanic said it was piston slap. I've never heard these motors had that problem and she is letting it go cheap ($6500) so i'm curious.