Sounds like a high speed whirring hum, right? I had the same problem with my 1958 235 several years ago. I took the starter in and had it rebuilt. I can't remember what the specific diagnosis was, but it boiled down to a weak starter. I want to say it had soemthing to do with the bendix, but again I just can't remember anymore. Once I had it rebuilt, it worked fine. I've had the same issue with a different vehicle in the past few years, too.
