I wouldn't go over 220 duration. I've seen a few with higher stalls and it didn't work so well. I don't know how their stall was set up though. I'm assuming loose because it would keep climbing in rpms until it went and it seemed like they were dumping the clutch on a manual trans. Depending on gear reduction a stall won't be as beneficial either. Me personally, I wouldn't run a cam that needed a large stall.