Looking for a double roller for a slant 6

On a related subject......has anyone ever lost a chain in a slant 6?? I've been playing with these things for over 40 years now and have NEVER seen a broken chain or one that has skipped. I've had ones so loose they hit the timing cover and caused the ignition timing to vary almost 30 degrees but they still worked. Maybe I've just led a sheltered life...... :-)