What is the differance with a ls3, l92 piston? Will regular flat tops work with those heads? Are the valve pockets offset or something? Some manufactures have ls3,l92 specific pistons. Why?

 

L92's run VVT so the pistons have exhaust valve reliefs. LS3 are flat tops.

 

This is correct...
Becasue L92/LS3 heads use a 2.160" valve, which is much larger than the standard 2.000" valve in most cathedral port LS heads. They have to make the valve relief larger knowing its going to be used in conjunction with a very large valve.

 

Theres also two valve reliefs per piston which equate to -4cc.

 

Bingo!
Valve reliefs on both intake and exhaust

 

Actually its just for the intake. However they only manufacture one type so each piston has an extra intake valve relief on the opposite side.

 

Sorry to revive an old thread but if I delete my vvt can I run the oem ls3 flat tops in my L92 with the L92 823 heads? Block and head surfaces are stock and using factory mls ls3 headgaskets. Greatly appreciate any help on this.

 

YES. YOU CAN RUN LS3 PISTONS (flattops). Just be curtain to mic the cylinders and pistons. If they check out ok, you might want to have a machine shop cut valve reliefs.