A Mod Engine rules

[BTExpress]

I am a fairly new fan to the world of A Mod racing. In simple terms, what are the differences in engine rules between the 4 national sanctioning bodies. I know IMCA runs 604 Crate motors. But what about UMP, USRA/USMTS and Wissota? Does a team have to make many changes to run races between the series? Have there been discussions in the past about bringing the rules packages closer together nationally like there is in Super Late Models, or are egos in the way?

[Mod Runner]

Basically, all sanctioning bodies allow open motors with no cubic inch limit. IMCA does not allow aluminum heads on open motors , but crate motors can run aluminum heads. USMTS/USRA have spec motors that have limitations on how much horsepower thy can produce but they get a weight break and can have aluminum heads. Open motors with aluminum heads require weight to be added to the front of the race car.

[BTExpress]

Mod Runner, Thank you. A concise and easy to understand explanation.