Regardless of the discussion about cone bolts etc, just think of the inertia of a JT8 at T/O power!! The gyroscopic effect would send it miles until it ran down!!
Well we do have lots of experience good and bad with this sort of thing, some of which IGH has already posted.
Engines which toss their cookies before breaking off have already lost much of their inertia by the time that they fall away so no big gyro there (Kalita B747).
Engines which are perfectly good and fall away (fatigue of pylon mounts) have enough fuel left in their guts to last about 5 secs. The smaller engines (on the B737) simply fall away even at takeoff/early climb power having been found pretty much on the runway heading within walking distance from the point of departure.
The larger fan engines like the JT3D on the B707 act just like the JT9D on the B747 (El AL, CI) and being released due to pylon mount fatigue lift up and snap to the right into the outboard engine due to gyro loading effects within the first 5 sec.