when a 400 gets bored 30 over, what size does that make the engine? My dads yard truck has a 400 bored 30 over and is going to put it in his f-250. I don't know anything much when it comes to this. Nice soundin motor. Not to many miles since the rebuilt. He got the complete truck for $1000, worth it alone just for the motor. It was rebuilt by a authorized Ford company. That's what the tag on the inner fender says. A company out of Winnipeg Ma, Canada.