It could need .060" and still not smoke to bad. If the rings were good and all the seals tight it might not smoke at all. Also if the valves were sealed tight, the compression could leak past the rings and this could keep the oil out. Take you manual back with you and remeasure the holes at the top just under where the ring ridge is.
Another way to look at it is, the bigger the hole the more cubic inches which means more power!!
Joe
