I have the newer version of the SB2.2 heads from Childress racing. I upgraded from the older version I had a few months ago to this set with a better exhaust port. These are the 011 castings from 2003. They maxed out at 401 cfm at .700 on the intake and 286 at .700 on the exhaust. With a pipe on the exhaust they flowed nearly 300cfm. The new motor will be a 401ci, 4.125 bore with Crower 3.75 stroke from the old motor and have the new Oliver Super Speedway Billet rods. Pistons are from Venolia. It should be good for 2000hp even with the 94mm reducer required by my racing org in my PT 106.