The intros and outros to many scenes were cut, leaving the middles - as well as dropping entire sequences, and trims to violent content and creature footage.
According to various interviews, about 4 hours, 3 1/2 hours, 3 hours, 2 1/2 hours-long originally.
The final preview cut removed 11 minutes, whittling it down to the now 116 minutes 1979 theatrical release.