Another difference between then and now... back then the Century used Grand Central Terminal and LaSalle Street Station, although not sure if that makes any difference in running time...
Probably the biggest delay for the Lake Shore, is the time spent at ALB for switching in/out the Boston section...
Well, in today's schedules the LSL takes 46 minutes to get from Penn to Croton, and the one-stop Metro-north trains take 46 minutes from Grand Central to Croton. But if you have ever sat at 125 St. waiting for a train, you know that the Metro-north stops there are super quick.
According to the 20th Century timetable posted further down this thread, the 20th century took 46 minutes from Grand Central to Croton _including the engine change at Croton_.
So one might conclude that the change from Grand Central to Penn did not have a big effect on the schedule, but the generally slower running these days maybe has had some effect.
(Without checking, I recall that the Metro-north schedule was lengthened by five minutes or so after the Spuyten-duyvil crash a few years back.)
Finally, when I last rode the LSL a few years ago the double spots at many stations seemed crazily time consuming. Without any actual data, it seemed like the train sat at each spot for about ten minutes. That adds up!
Ainamkartma
Edited to repair basic math errors. Lordy!