Which could mean anything from broken rings, head gasket, vavle stem seals, cracked head... anything that could let oil into the combustion chamber and get burnt, so blue smoke out the rear.
It's a crate motor it's been put it the car sat in the shed for about a year then after driving it for like a months it's done this ? So I can't see how it's a cracked head or any of that. Maybe a sticky valve ?