Things varied from year to year. (Source ... July 1953 Official Guide.)
Westbound, the BUILDER left Chicago at 1:00 PM on CB&Q rails. Arrival at St. Paul was 7:45 PM; departure was 8:15 PM. Departure from Minneapolis was 8:45 PM. Spokane was reached by 11:30 PM the next evening. Arrival in Seattle and/or Portland was at 7:30 AM.
Eastbound, the BUILDER departed Seattle and/or Portland at 3:00 PM. Spokane was reached at 11:15 PM. Arrival in Minneapolis was at 6:30 AM; St. Paul at 7:00 AM. Departure from St. Paul (on the CB&Q) was at 7:15 AM, with a 2:00 PM arrival time in Chicago.
Between Chicago and Minneapolis, the EMPIRE BUILDER, NORTH COAST LIMITED and the MORNING/AFTERNOON ZEPHYRs were all listed as separate trains.
The BUILDER was just receiving it's new post-war equipment around this time, and it's old(er) post-war trainsets moved over to the WESTERN STAR.
You didn't ask, but, at this date, the westbound WESTERN STAR departed Chicago (on the CB&Q) at 10:50 PM. St. Paul was reached at 8:00 AM the next morning; Minneapolis at 8:30 AM. Spokane was reached at 9:30 PM the next evening. Seattle and/or Portland arrival 7:00 AM.
Eastbound, the STAR left Portland at 9:30 PM and/or Seattle at 10:15 PM. Spokane was reached by 7:20 AM the next morning. Arrival in Minneapolis was at 9:55 PM the next evening; St. Paul at 10:30 PM. Chicago was reached by 7:30 AM the next morning via the CB&Q.
At this time, the WESTERN STAR was listed as a separate train from CB&Q's BLACK HAWK, although NP's MAINSTREETER was combined with the BLACK HAWK.
I don't have an earlier guide; but, I hope this helps, and give you some idea of timings.