At the recent NORRCA nats, there wasn't any clarity on this. We were told 38oz for all Expert classes, and 40 for sportsman. Then at the tech table during the event, they said that all mod classes were 38oz. I confirmed it with them several times and then pulled the lead out of my car. The NORRCA oval rules haven't really been updated and set in stone for 2004 - they seem to be variable depending on when you ask and who you ask. The official rules on their website are 2 years old and out of date. If you go by that, then 3300mah batteries are illegal too. They need to be updated.