Gone from an 07 Z51 to 13 GS and I've noticed that my LS2 engine idled very smoothly compared to the LS3 engine. The LS3 engine feels like it is loping and I wonder if that is due to perhaps a "hotter" cam and if all LS3 engines do this.

 

My LS3 is rougher then my LS2 GTO was when it was stock.

 

My 2011 LS3 idles more rumbly than my 2007 LS2 did. Stock exhaust on both.

 

A slightly Larger bore, bit more cam. Nothing to worry about.

 

My '08 LS3 must just be a puppy, it's smooth at idle. Oh,of course, it's a standard C6.

 

I too have gone from a '07 LS2 to a '13 LS3 and notice the same, a bit more rough/lopy idle and a more pronounced tick noise(lifter or injector) not concerned though after all 430 hp should make some noise.

 

Real rough in the morning and then it gets a little better ,until the lifters start clattering.Then I dump in a bottle of ZMax in and it is a little quiter.
Others have told me it is the cam but that one is up to you.

 

A little idle lope/roughness is normal for the LS3.

Or you might have an easily-fixed issue, like a dirty MAF sensor.

Other possibilities & discussion:
http://forums.corvetteforum.com/c6-c...ough-idle.html

 

hmmm noticed the same going from a LS3 to a LS7