I have never experienced a positive outcome cold bending cast steel parts, I heat them first then bend while hot. You just never know what the steel will do. It takes some extra time and it is a pain but so far have not broken anything since I started taking the time to heat first. If I am in a hurry I allow them to cool down to around 300 degrees before quenching, that low of a temp doesn`t seem to make much difference unless it is intentional in the heat treating process.