Welcome to the fun of printing with ABS. I've had many parts split, and many parts not split. It depends on many factors, and the shape of the part has a huge effect. I typically print ABS at around 240C.
Be careful with a heat box, as this can start to get into the softening zone for printer parts made out of PLA. I tried this, and was using a Wade's extruder. The gear mounted to the stepper shaft softened, and started slipping due to the increased ambient temperature, which raised the stepper temperature enough to really soften the gear.
Mike