I was just looking in an 05 Firebolt parts catalog, and noticed there are different p/n's for the XB9 and the XB12 pistons. Anyone know how they are different? They are the same bore size 3.50 and the same compresstion is run in both bikes 10:1. so what is the dif? Maybe the NRHS guys will know.

The only thing that I can think of is that maybe the skirt is shorter to accomodate the shorter stroke in the XB9's.

Are they cast or forged? Anyone know the info.?

The XB9 is a short stroke version of the XB12 motor (3-1/8 stroke vs 3-13/16 stroke).

As such, if a 12 piston were used in a 9, the compression ratio would be very low. Remember, compression ratio is the ratio of volume above the piston at BDC over volume above the piston at TDC. The difference between those two volumes of the is the displacement. So less displacement = less compression if you use the same dome and chamber.

The 9's piston has a dome.